Bulletin  51 
"T  p 

BUREAU     OF     MINES 

JOSEPH  A.  HOLMES,  DIRECTOR 


5s 


THE  ANALYSIS  OF 
BLACK  POWDER  AND  DYNAMITE 


BY 


WALTER  O,  SNELLING  AND  C.  G.  STORM 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 
1913 


Bulletin  51 

DEPARTMENT   OF   THE    INTERIOR 
BUREAU     OF     MINES 

JOSEPH  A.  HOLMES,  DIRECTOR 


THE  ANALYSIS  OF 
BLACK  POWDER  AND  DYNAMITE 


BY 


WALTER  O.  SNELLING  AND  C.  G.  STORM 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 
1913 


First  edition.     March  ,1913. 


Ml 


CONTENTS. 


Page. 

In  troduction 5 

Dynamite 6 

Physical  examination 7 

Determination  of  gravimetric  density 7 

Test  for  liability  of  exudation 

Forty-degree  test  for  exudation 8 

Pressure  test  for  exudation 9 

Centrifugal  test  for  exudation 9 

Test  for  stability 10 

Abel  test 10 

Caramel  standard  tint  paper 11 

Preparation  of  paper  for  Abel  tes 12 

Sampling 12 

Chemical  examination 16 

Qualitative  examination 16 

Determination  of  moisture 19 

In  ordinary  desiccators 20 

In  vacuum  desiccators 27 

In  a  dry-air  current 28 

Summary 29 

Extraction  with  ether 30 

Reflux-condenser  method 30 

Suction  method 32 

Comparative  extractions  with  anhydrous  and  U.  S.  P.  (96  per  cent) 

ether 33 

Effect  of  moisture  in  dynamite  on  extraction  with  ether 34 

Determination  of  nitroglycerin 35 

The  nitrometer 35 

Procedure 38 

Evaporation  in  the  bell-jar  evaporator 40 

Determinations  of  sulphur,  resins,  etc 41 

Extraction  with  water 43 

Determination  of  alkaline  nitrates 44 

Determination  of  alkaline  nitrates  by  means  of  the  nitrometer 45 

Extraction  with  acid 45 

Determination  of  calcium 46 

Determination  of  magnesium 46 

Determination  of  zinc 46 

Determination  of  starch 47 

Examination  of  insoluble  residue 49 

Determination  of  wood  pulp,  etr 49 

Determination  of  ash 50 

Variations  due  to  method  of  analysis 50 

Discussion  of  analyses 52 

Moisture 52 

Nitroglycerin 52 

Potassium  nitrate 53 

Calcium  carbonate 53 

Wood  pulp 53 

M1S5892 


CONTENTS. 


Gelatin  dynamite 

Sampling 

Sulphur 

Nitrocellulose 

Ammonia  dynamite 

Low-freezing  dynamite 

Determination  of  nitrosubstitution  compounds 

Granulated  nitroglycerin  powder 

Black  powder 

Physical  examination 

Granulation  or  average  size  of  grains 

Gravimetric  density 

Absolute  density 

Sampling 

Chemical  examination 

Determination  of  moisture 

Extraction  with  water;  determination  of  nitrates 

Extraction  with  carbon  disulphide;  determination  of  sulphur. 

Insoluble  residue,  charcoal 

Determination  of  ash 

Bureau  of  Mines  method  of  analysis 

Publications  on  mine  accidents  and  tests  of  explosives 


ILLUSTRATIONS. 


PLATE  I.  A,  Apparatus  for  Abel  heat  test;  B,  Centrifuge  for  exudation  test  of 

dynamite 10 

II.  A,  Wiley  extractor;  B,  Gravimetric  balance 32 

III.  Nitrometer 36 

IV.  A,  Wood  pulp  No.  1;   B,  Wood  pulp  No.  2;    C,   Sawdust;    D,  In- 

fusorial earth  No.  1;  E,  Infusorial  earth  No.  2;  F,  Crude  fiber  from 

wheat  middlings 50 

V.  A,   Cellulose   (cotton);    B,   Nitrocellulose;     C,   Wheat  flour  (fine); 
D,  Wheat  flour  (fine)  and  wood  pulp;    E,  Wheat  flour  (middlings); 

F,  Corn  meal 52 

FIGURE  1.  Influence  of  temperature  on  determination  of  moisture  in  60  per  cent 

dynamite  by  desiccation  over  sulphuric  acid 23 

2.  Results  of  desiccation  of  60  per  cent  dynamite  over  calcium  chloride 

and  over  sulphuric  acid  at  room  temperatures 25 

3.  Result  of  exposure  of  dry  60  per  cent  dynamite  in  a  desiccator  at 

33°  to  35°  C.  without  desiccating  agent 26 

4.  Drying  tube 30 

5.  Densimeter...  68 


THE  ANALYSIS  OF  BLACK  POWDER  AND  DYNAMITE. 


By  WALTER  O.  SNELLING  and  C.  G.  STORM. 


INTRODUCTION. 

Although  descriptions  of  the  methods  of  analysis  of  explosives  are 
to  be  found  in  many  books  on  explosives,  and  in  works  on  engineer- 
ing chemistry  or  chemical  analysis,  most  of  these  descriptions  are 
incomplete  and  lacking  in  details.  The  methods  of  analysis  employed 
in  the  laboratories  of  most  explosives  factories  are  frequently  treated 
as  trade  secrets,  and  very  little  information  is  published  from  such 
laboratories. 

This  bulletin  ou times  the  methods  of  analysis  that  are  used  by 
the  Bureau  of  Mines  in  the  examination  of  certain  classes  of  explo- 
sives. The  present  form  of  most  of  these  methods  has  been  worked 
out  in  the  bureau's  explosives  laboratory.  The  methods  employed 
by  Prof.  C.  E.  Munroe  were  taken  as  a  basis,  and  were  elaborated  to 
meet  the  demands  incident  to  the  treatment  of  complicated  mix- 
tures and  to  the  development  of  the  explosives  art.  A  subsequent 
bulletin  will  discuss  the  methods  of  analysis  of  "permissible" 
explosives,  many  of  the  latter  being  of  decidedly  complicated  char- 
acter and  requiring  special  treatment.  This  bulletin  presents  the 
methods  of  analysis  of  "ordinary"  dynamite,  and  the  ammonia, 
gelatin,  low-freezing,  and  granular  dynamites,  and  the  common 
grades  of  black  gunpowder  and  black  blasting  powder.  The  bulletin 
is  published  by  the  bureau  for  the  information  of  all  persons  inter- 
ested in  explosives  and  their  safe  and  efficient  use  in  mining  work. 

As  the  term  "ordinary"  dynamite,  though  much  used,  has  no 
conventional  meaning,  and  may  be  used  to  cover  a  wide  variety  of 
compositions  of  matter,  it  may  be  noted  that  the  standard  dynamite 
used  at  the  Pittsburgh  testing  station  is  a  good  example  of  the 
"ordinary"  dynamite  known  in  this  country.  This  testing  station 
dynamite  has  the  following  composition: 

Composition  of  Pittsburgh  testing  station  dynamite. 

Per  cent. 

Nitroglycerin 40 

Sodium  nitrate 44 

Wood  pulp 15 

Calcium  carbonate 1 

5 


6  V:  ANALYSIS   OF   BLACK   POWDEK  AND   DYNAMITE. 

As  mos-;  permissible  explosives  contain  only  the  constituents 
found  generally  in  cthe  various  types  of  ordinary  dynamite,  the 
chemist  will  usually  find  it  possible  to  analyze  such  explosives  either 
wholly  or  partly  by  following  the  general  methods  of  analysis  here 
given  for  the  type  of  explosive  that  seems  most  closely  related  to  the 
one  under  examination.  The  methods  of  extraction  with  ether, 
with  water,  etc.,  here  outlined  are  general  methods  which  are  applied 
with  equal  success  to  all  classes  of  explosives,  and  therefore  by  the 
use  of  these  general  methods,  following  a  thorough  qualitative 
examination,  little  difficulty  should  be  met  except  with  those  classes 
of  permissible  explosives  that  contain  large  amounts  of  salts  holding 
water  of  crystallization,  such  as  alum  and  magnesium  sulphate,  or 
those  containing  an  unusual  number  of  uncommon  constituents. 
Even  with  such  explosives,  however,  if  the  information  desired  is 
principally  in  regard  to  the  percentages  of  explosive  ingredients 
(nitroglycerin,  ammonium  nitrate,  etc.),  the  methods  outlined  in 
this  bulletin  may  be  satisfactorily  followed. 

DYNAMITE. 

"Ordinary"  dynamite  consists  essentially  of  nitroglycerin  absorbed 
in  some  porous  material.  Owing  to  its  physical  condition  and  its 
extreme  sensitiveness  to  shock,  liquid  nitroglycerin  is  not  suitable 
for  use  as  an  explosive  in  mining  and  quarrying,  but  when  nitro- 
glycerin is  absorbed  in  a  porous  material  a  more  or  less  plastic  mass 
is  obtained  which  is  far  less  sensitive  to  shock  than  liquid  nitro- 
glycerin, although,  when  properly  fired  by  means  of  a  detonator,  it 
retains  most  of  the  explosive  properties  of  nitroglycerin.  Among 
the  many  substances  that  have  been  used  as  absorbents  for  nitro- 
glycerin are  sawdust,  wood  pulp,  ground  mica,  and  infusorial  earth 
(kieselguhr),  or  mixtures  of  these  substances  with  alkaline  nitrates 
and  other  substances. 

It  is  usual  to  classify  absorbents  for  nitroglycerin  as  active  and 
inactive.  Pulverized  gunpowder,  for  example,  or  mixtures  of  wood 
pulp  with  sodium  nitrate  or  other  oxidizing  agents,  represent 
"  active"  absorbents,  whereas  mica,  kieselguhr  and  similar  materials, 
which  play  no  part  in  the  explosive  reactions  and  which  are  employed 
merely  to  absorb  or  retain  the  liquid  nitroglycerin,  form  the  so-called 
" inactive"  absorbents. 

The  type  of  dynamite  most  generally  used  to-day  consists  of  nitro- 
glycerin absorbed  in  a  mixture  of  wood  pulp  and  sodium  nitrate, 
and  to  this  mixture  is  usually  added  a  small  amount  of  some  antacid 
such  as  calcium  carbonate,  magnesium  carbonate,  or  zinc  oxide. 
This  antacid  is  added  in  the  belief  that  it  increases  the  stability  of 
the  resulting  explosive  by  neutralizing  such  small  amounts  of  free 


DYNAMITE.  7 

acid  as  may  be  produced  by  the  decomposition  of  the  nitroglycerin 
during  long  storage. 

The  analysis  of  dynamite  is  best  carried  out  by  first  separating, 
with  ether  or  some  other  appropriate  solvent,  the  nitroglycerin  from 
the  dope  in  which  it  is  absorbed.  After  the  nitroglycerin  has  been 
thus  removed,  the  soluble  nitrate  in  the  dope  may  be  removed  by 
dissolving  in  watrr;  the  antacid  may  then  be  dissolved  in  dilute 
acid,  and  the  residue  insoluble  in  ether,  water,  dilute  acid,  etc., 
may  be  directly  determined  by  weight. 

In  its  simplest  form,  therefore,  the  analysis  of  dynamite  consists 
in  the  removal  of  the  constituent  materials,  one  by  one,  through  the 
use  of  appropriate  solvents.  Dynamites  of  the  most  complicated 
composition  may  usually  be  analyzed  in  this  way,  through  selective 
solution.  In  the  present  paper  the  methods  of  analyzing  ordinary 
types  of  dynamite  are  discussed,  and  those  that  have  been  found 
best  in  an  experience  covering  several  thousand  analyses  are  stated. 

PHYSICAL  EXAMINATION. 

Upon  receiving  a  sample  of  explosive  for  analysis  it  is  desirable 
to  record  full  information  in  regard  to  the  size  and  weight  of  each 
cartridge,  with  a  complete  copy  of  any  lettering  that  may  appear  on 
the  wrapper.  It  is  also  advisable  to  record  the  nature  of  the  outer 
wrapping  paper  (such  as  ordinary  paper,  parchmentized  paper, 
or  paper  coated  with  paraffin),  and  whether  the  cartridge  has  been 
redipped;  that  is,  placed  in  a  paraffin  bath  after  being  filled. 
Whether  a  cartridge  has  been  redipped  can  usually  be  determined 
by  carefully  opening  the  wrapper.  If  there  is  a  greater  thickness 
of  paraffin  near  the  edge  where  the  sheet  overlaps,  or  if  the  overlap- 
ping edge  is  attached  to  the  adjacent  portions  of  the  paper  by  means 
of  an  adhering  deposit  of  paraffin,  it  may  be  assumed  that  the  cart- 
ridge has  been  redipped. 

DETERMINATION    OF    GRAVIMETRIC    DENSITY. 

It  is  possible  to  determine  approximately  the  gravimetric  density 
or  apparent  specific  gravity  of  a  cartridge  of  explosive  by  measuring 
carefully  the  length  and  circumference  of  the  cartridge,  calculating 
from  these  figures  the  volume  in  cubic  centimeters,  and  then  dividing 
the  weight  in  grams  of  the  cartridge  by  this  figure.  However, 
experiments  made  at  the  bureau's  explosives  laboratory  have  shown 
that  even  with  the  most  careful  measurements  the  figures  thus 
obtained  are  liable  to  be  in  error  by  as  much  as  10  to  20  per  cent, 
a  difference  entirely  too  great  to  make  the  method  permissible  for 
exact  work.  With  some  redipped  cartridges  weighing  in  water  has 
given  satisfactory  results,  but  cartridges  seldom  have  a  coating  of 


8  ANALYSIS   OF  BLACK  POWpEK  AND  DYNAMITE. 

paraffin  so  complete  as  to  permit  the  use  of  this  method.  Accord- 
ingly a  method  was  sought  that  would  at  all  times  give  satisfactory 
results  even  with  cartridges  that  had  not  been  redipped. 

The  volume  of  the  cartridge  can  be  determined  conveniently 
by  using  sand  instead  of  water  as  the  measuring  material.  A 
weighed  glass  cylinder  about  30  cm.  high  and  5  cm.  in  inside  diameter 
is  filled  with  fine  sand  (preferably  sea  sand)  .that  has  been  sifted 
through  a  60-mesh  sieve.  A  straight  edge  is  drawn  across  the  top 
of  the  cylinder,  the  level  of  the  sand  being  left  flush  with  the  top 
edge,  and  the  weight  of  the  cylinder  and  contained  sand  is  determined. 
From  this  weight  the  weight  of  the  cylinder  is  subtracted  and  the 
result  is  the  weight  of  the  sand,  which,  divided  by  the  weight  of 
water  required  to  fill  the  cylinder,  gives  the  apparent  specific  gravity 
of  the  sand  used.  All  the  sand  except  enough  to  fill  the  cylinder  to 
a  depth  of  about  1  inch  is  now  poured  out,  a  weighed  cartridge  of 
the  explosive  is  placed  in  the  cylinder,  and  sand  added  until  the 
cylinder  is  filled  flush  to  the  top  as  before,  when  it  is  struck  with  the 
straight  edge  and  then  the  weight  of  cylinder  and  sand  and  cartridge 
is  noted.  From  these  figures  the  weight  of  sand  displaced  by  the 
cartridge  is  found.  This  weight  divided  by  the  apparent  specific 
gravity  of  the  sand  gives  the  volume  of  the  cartridge.  The  weight 
of  the  cartridge  divided  by  its  volume  gives  its  apparent  specific 
gravity  or  gravimetric  density.  This  determination  leaves  the  car- 
tridge in  condition  for  use  in  sampling,  if  desired. 

In  making  this  determination  care  should  be  taken  that  the  cylinder 
is  filled  each  time  in  exactly  the  same  manner,  the  sand  being  poured 
in  slowly  and  not  packed  by  jolting,  shaking  or  otherwise.  Repeated 
determinations  of  the  weight  of  sand  required  to  just  fill  the  cylinder 
will  prove  that  with  proper  care  uniform  results  may  be  obtained;  in 
practice  this  method  has  been  found  to  be  both  rapid  and  exact. 

TEST   FOR    LIABILITY   OF    EXUDATION. 

To  determine  whether  there  is  liability  of  leakage  of  nitroglycerin 
from  cartridges  containing  this  explosive,  it  is  always  advisable  to 
make  an  exudation  test,  which  indicates  the  amount  of  nitroglycerin 
that  may  be  lost  by  the  explosive  tested  under  prescribed  condi- 
tions. The  tests  most  commonly  used  for  this  purpose  are  the  40° 
test,  the  pressure  test,  and  the  centrifugal  test. 

40°  TEST  FOR  EXUDATION. 

In  the  40°  test  a  cartridge  of  the  explosive  under  examination  is 
placed  in  a  vertical  position  in  an  oven  heated  to  40°  C.  Some  small 
perforations  are  made  in  the  wrapper  at  the  ends  of  the  cartridge, 
and  the  cartridge  is  then  placed  on  end  on  a  small  wire  tripod  in  a 


DYNAMITE.  9 

small  glass  beaker  or  cylinder.  The  whole  is  then  placed  for  six  days 
in  an  oven  maintained  at  a  constant  temperature  of  40°  C.  At  the 
end  of  this  time  an  examination  is  made  to  see  if  any  leakage  of 
nitroirlyoerin  in  the  form  of  drops  has  occurred.  Such  leakage  may 
be  taken  as  evidence  that  there  is  too  much  nitroglycerin  in  the 
explosive  for  the  amount  of  absorbent  material  present,  or  that  the 
dope  used  is  deficient  in  absorbing  capacity. 

PRESSURE   TEST   FOR   EXUDATION. 

Before  the  centrifugal  test  was  employed,  it  was  customary  to  use  a 
pressure  test  for  exudation  which  consisted  in  exposing  a  sample  of  the 
dynamite  to  a  definite  pressure  produced  by  a  weight  on  a  lever  arm, 
and  determining  the  amount  of  nitroglycerin  thereby  forced  out  of 
tho  dynamite.  Many  modifications  of  this  test  have  been  tried,  in 
which  cotton,  blotting  paper,  or  other  absorbent  material  have  been 
used  to  hold  the  nitroglycerin  forced  out  from  the  explosive.  The 
pressure  test  is  unreliable  and  hence  is  not  satisfactory  in  use.  For 
example,  by  this  test  an  explosive  that  contains  a  certain  amount  of 
a  mixture  of  sawdust  and  wood  pulp  shows  less  exudation  than  one 
in  which  the  same  amount  of  absorbent  is  used  in  the  form  of  wood 
pulp  alone,  a  result  that  is  clearly  incorrect,  since  the  absorbing 
power  of  wood  pulp  is  much  greater  than  that  of  sawdust.  The  reason 
for  the  more  favorable  result  when  the  absorbent  contains  sawdust  is 
that  the  particles  of  sawdust  are  packed  together  to  form  a  cellular 
mass,  which  incloses  the  particles  of  wood  pulp  holding  the  nitro- 
glycerin, thereby  in  a  great  measure  protecting  them  from  pressure. 

CENTRIFUGAL   TEST   FOR    EXUDATION. 

The  use  of  centrifugal  force  as  a  means  of  measuring  the  complete- 
in  •«  with  which  nitroglycerin  is  absorbed  in  an  explosive  was  some 
years  ago  suggested  to  Col.  B.  W.  Dunn,  chief  inspector  of  the  bureau 
for  the  safe  transportation  of  explosives,  by  T.  J.  Wrampelmeier,  an 
inspector  in  that  bureau,  and  a  device  for  testing  the  value  of  this 
method  was  made  use  of  by  C.  P.  Beistle,0  chief  chemist  of  that 
bureau.  The  method  employed  was  to  place  the  explosive,  together 
with  a  perforated  disk  of  vulcanite  and  an  absorbent  material  such 
as  cotton,  within  a  glass  tube,  the  tube  being  then  placed  in  a  cen- 
trifuge. The  increase  in  weight  of  the  cotton  after  rotation  was 
taken  as  a  measure  of  the  amount  of  nitroglycerin  lost  by  the  explo- 
sive during  the  process.  This  apparatus  gives  much  more  satisfac- 
tory results  than  the  former  methods  of  testing  by  pressure  alone,  but 
owing  to  the  fact  that  the  cotton  becomes  compressed  during  rotation, 
thus  changing  the  position  of  the  vulcanite  disk,  the  apparatus  at 

•  Report  of  chief  inspector  of  the  bureau  for  the  safe  transportation  of  explosives,  February,  1909. 


10  ANALYSIS   OF   BLACK   POWDER  AND   DYNAMITE. 

times  gives  discordant  results,  and  the  figures  from  tests  of  any  two 
explosives  are  not  proportional  to  the  relative  tendency  toward  leakage 
of  nitroglycerin  under  normal  conditions. 

One  of  the  authors  designed  a  centrifuge  attachment  which  is  now 
being  used  with  reliable  results  by  the  Bureau  of  Mines.  This  appa- 
ratus is  shown  in  Plate  I,  A.  Two  samples  of  the  explosive  are  placed 
in  ordinary  porcelain  Gooch  crucibles,  without  mat,  the  crucibles  being 
held  above  two  other  nonperforated  crucibles  in  the  manner  shown. 
A  small  amount  of  cotton  is  placed  in  each  of  the  lower  crucibles  to 
receive  the  exuded  nitroglycerin,  and  the  loss  by  exudation  is  deter- 
mined by  weighing  the  crucibles  containing  the  explosive  before  and 
after  rotation.  The  circle  of  rotation  made  by  the  bottom  of  the 
crucibles  is  14  cm.  in  diameter,  and  the  standard  velocity  of  rotation  is 
600  revolutions  (30  turns  of  the  handle)  per  minute.  The  usual  test 
consists  in  placing  8  grams  of  explosive  in  each  of  the  upper  crucibles, 
and  determining  the  loss  in  weight  after  rotating  at  the  velocity  of 
600  revolutions  per  minute  for  5  minutes  at  a  temperature  of  about 
20°  C.  If  the  explosive  does  not  lose  more  than  5  per  cent  in  weight 
it  is  considered  to  have  satisfactory  absorbing  capacity,  but  if  more 
than  5  per  cent  is  lost  its  absorbent  properties  are  considered  defi- 
cient, and  in  the  transportation  or  use  of  such  an  explosive  there  is 
considered  to  be  liability  of  accident. 

TEST    FOR    STABILITY. 

Many  tests  have  been  proposed  for  determining  the  stability  of 
explosives  under  the  influence  of  heat,  and  much  has  been  written  in 
regard  to  the  comparative  accuracy  of  these  different  tests.  This 
field  is  now  being  investigated  by  the  bureau,  and  a  special  report 
thereon  will  be  issued.  At  present  all  mining  explosives  examined 
by  the  bureau  are  tested  for  stability  by  means  of  the  Abel  heat  test. 


ABEL    TEST. 


The  Abel  stability  test  depends  upon  the  fact  that  when  potassium 
iodide  is  decomposed  in  the  presence  of  starch,  the  iodine  liberated 
reacts  with  the  starch  to  form  a  colored  body.  The  explosive  to 
be  tested  is  placed  in  a  stoppered  test  tube  and  heated  in  a  constant- 
temperature  bath  until  the  oxides  of  nitrogen  liberated  as  de- 
composition products  make  a  brownish  color  on  a  strip  of  potassium 
iodide  starch  paper  suspended  in  the  tube  above  the  explosive. 
The  stability  of  the  explosive  is  judged  by  the  time  required  for  the 
production  of  a  coloration  of  a  standard  intensity.  The  apparatus 
used  in  the  Abel  test  is  illustrated  in  Plate  I,  A. 

Two  grams  of  explosive  in  its  original  condition,  without  prelimi- 
nary drying  or  preparation  other  than  thorough  mixing,  is  placed  in 


DYNAMITE.  11 

a  glass  tube.  The  tube  is  of  standard  dimensions  as  follows:  Length, 
14  cm.  (5J  inches);  inside  diameter,  not  less  than  1.27  cm.  (£  inch); 
outside  diameter,  not  more  than  1.59  cm.  (f  inch);  thickness  of  the 
glass,  about  1.2  mm.  (^  inch).  The  tube  is  closed  by  a  clean, 
tightly  fitting  cork  stopper,  through  which  passes  a  glass  rod  pro- 
vided with  a  platinum  hook,  fused  into  the  lower  end  for  holding  the 
test  paper.  The  test  papers,  in  pieces  about  2.5  cm.  (1  inch)  by  1.0 
cm.  (f  inch),  are  hung  on  the  platinum  hooks  (forceps  being  used 
in  handling)  and  the  upper  half  of  each  strip  of  test  paper  is 
moistened  with  a  solution  of  equal  volumes  of  pure  glycerin  and 
water. 

The  test  paper  used  is  potassium  iodide  starch  paper,  similar  to 
that  prepared  by  Eimer  &  Amend  (Frankford  Arsenal  formula),  or 
prepared  by  a  standard  method  as  described  below.  The  heat-test 
bath  is  placed  so  that  a  good  light — not  direct  sunlight — is  trans- 
mitted through  the  test  papers  to  the  operator.  The  bath  tempera- 
ture is  maintained  constant  within  0.5°  C.  of  the  desired  temperature 
(71°  C.),  the  thermometer  being  so  immersed  that  the  bottom  of  the 
bulb  is  2£  inches  below  the  top  of  the  bath. 

All  determinations  are  made  in  duplicate.  The  shorter  tune 
required  to  bring  one  of  the  two  test  papers  to  the  prescribed  tint 
determines  the  test  of  the  explosive,  except  in  case  of  wide  variation 
in  results,  when  two  or  more  additional  samples  are  tested. 

After  each  test  the  cork  stopper  of  each  tube  is  either  discarded  or 
carefully  washed  and  dried  and  in  any  case  is  frequently  renewed. 
The  tube  and  the  rod  are  carefully  cleaned  after  each  test,  ether  or 
other  solvent  being  used  to  remove  nitroglycerin,  etc.  They  are 
then  washed  with  water,  and  finally  rinsed  with  distilled  water. 
All  the  parts  of  the  apparatus  are  dried  in  a  steam  oven  at  100°  C. 
The  apparatus  is  at  all  times  protected  from  laboratory  fumes. 

The  tube  is  inserted  to  a  depth  of  2£  inches  below  the  top  of  the 
bath,  the  water  hi  the  bath  being  within  one-fourth  inch  of  the  top. 
The  time  of  placing  the  tube  in  the  bath  is  recorded,  and  the  test  is 
considered  completed  on  the  appearance  of  a  brownish  line  at  the 
lower  edge  of  the  moist  portion  of  the  paper,  of  the  same  intensity  as  the 
line  on  a  standard-tint  paper  prepared  as  described  below.  It  should 
be  noted,  however,  that  the  brownish  color  on  the  test  paper  may  at 
times  be  spread  over  a  considerable  portion  of  the  paper,  not  forming 
a  sharp,  well-defined  line.  The  operator  should  judge  what  would 
be  equivalent  to  the  standard  tint  over  a  width  of  one-half  to  1  mm. 

Caramel  standard  tint  paper* — The  tint  paper  used  as  a  standard 
color  comparator  for  the  test  is  made  as  follows:  A  solution  of  caramel 
in  distilled  water  is  prepared,  of  such  concentration  that  when 
diluted  to  100  times  its  volume  (10  c.  c.  diluted  to  1  liter)  the  tint  of 

•  30th  Ann.  Report  H.  M.  Inspector  of  Explosives,  1905,  p.  236. 


12  ANALYSIS  OF  BLACK  POWDER  AND  DYNAMITE. 

the  solution  equals  that  produced  by  the  Nessler  test  on  adding  2  c.  c. 
of  Nessler  reagent  to  100  c.  c.  of  water  containing  0.000075  gram  of 
NH3,  or  0.0002305  gram  of  NH4  Cl.  With  a  fine  brush  or  pen  dipped 
into  this  caramel  solution  fine  lines  are  drawn  on  strips  of  filter  paper 
(Schleicher  and  Schiill,  597).  These  strips  are  cut  to  the  size  of  the 
regular  test  papers  (1  inch  by  f  inch)  so  that  the  brown  line  crosses 
each  piece  near  the  middle  of  its  length.  The  line  should  be  %  to 
1  mm.  in  width  when  dry.  A  piece  of  this  standard  tint  paper 
should  be  placed  in  an  empty  tube  beside  those  being  tested,  so  that 
a  comparison  of  color  may  be  made. 

Preparation  of  test  paper  for  Abel  test" — The  paper  used  in  pre- 
paring the  test  paper  is  Schleicher  and  SchiilPs  filter  paper  597. 
This  is  cut  in  strips  about  6  by  24  inches,  and  after  being  washed  by 
immersing  each  strip  in  distilled  water  for  a  short  time  is  hung  up  to 
dry  overnight.  The  cords  on  which  the  paper  is  hung  are  clean 
and  the  room  is  free  from  fumes.  The  washed  and  dried  paper  is 
dipped  in  a  solution  prepared  as  follows : 

The  best  quality  of  potassium  iodide  obtainable  is  recrystallized 
three  times  from  hot  absolute  alcohol,  dried,  and  1  gram  dissolved 
in  8  ounces  of  distilled  water.  Cornstarch  is  well  washed  by  decanta- 
tion  with  distilled  water,  dried  at  a  low  temperature,  3  grams  rubbed 
into  a  paste  with  a  little  cold  water,  and  poured  into  8  ounces  of 
boiling  water  in  a  flask.  After  being  boiled  gently  for  10  minutes, 
the  starch  solution  is  cooled  and  mixed  with  the  potassium  iodide 
solution  in  a  glass  trough. 

Each  strip  of  filter  paper  is  immersed  in  the  above-mentioned 
mixture  for  about  10  seconds  and  is  then  hung  over  a  clean  cord  to 
dry.  The  dipping  is  done  in  a  dim  light  and  the  paper  left  overnight 
to  dry  in  a  perfectly  dark  room.  Every  precaution  is  taken  to 
insure  freedom  from  contamination  in  preparing  the  materials  and 
from  laboratory  fumes  that  might  cause  decomposition.  When 
dry  the  paper  is  cut  into  pieces  about  f  by  1  inch  and  is  preserved 
in  the  dark  in  tight  glass-stoppered  bottles,  the  edges  of  the  large 
strips  being  first  trimmed  off  about  one-fourth  inch  to  remove  por- 
tions that  are  sometimes  slightly  discolored.  When  properly  pre- 
pared the  finished  paper  is  perfectly  white,  any  discoloration  indi- 
cating decomposition  due  to  contamination. 

SAMPLING. 

The  first  step  to  be  taken  in  the  analysis  of  dynamite,  as  with  any 
other  material,  is  the  careful  preparation  of  a  sample.  Dynamite 
is  offered  in  commerce  in  the  form  of  cylindrical  " sticks7'  or  car- 
tridges, usually  three-fourths  inch  to  1|  inches  in  diameter  and  8 

•  Storm,  C.  G.,  Proc.  7th  Inter.  Congress  Applied  Chem.    1909;  Jour.  Ind.  and  Eng.  Chem.,  vol.  1, 
1909,  p.  802. 


DYNAMITE.  13 

inches  long.  For  special  work  dynamite  is  made  in  cartridges  up  to 
5  inches  in  diameter,  but  owing  to  restrictions  in  railroad  trans- 
portation the  length  of  cartridges  of  dynamite  does  not  vary  greatly, 
and  cartridges  over  8  inches  long  are  unusual. 

A  cartridge  of  dynamite  consists  of  a  c  vering  of  paper,  some- 
times waxed  or  parchmentized  and  often  coated  with  paraffin,  within 
which  the  dynamite  is  more  or  less  tightly  packed  to  give  it  the 
density  desired.  In  the  manufacture  of  dynamite  the  paper  " shell" 
is  first  made,  and  is  then  packed  with  the  explosive,  after  which  the 
cartridge  is  sometimes  "redipped,"  by  which  is  meant  that  the 
cartridge  is  plunged  into  a  bath  of  paraffin  heated  slightly  above  its 
melting  point.  The  paraffin  closes  any  openings  in  the  wrapper  and 
tends  to  make  the  cartridge  waterproof.  This  operation  of  "redip- 
ping"  is  of  interest  in  connection  with  the  analysis  of  explosives 
chiefly  because  of  the  opportunity  it  affords  for  the  entrance  of 
paraffin  into  the  explosive.  When  a  paper  shell  is  not  perfectly 
made  some  paraffin  is  apt  to  find  its  way  through  the  paper  shell 
and  be  absorbed  by  the  wood  pulp.  In  sampling,  care  should 
always  be  taken  to  remove  any  paraffin  that  has  found  access  through 
the  ends  of  the  cartridge,  since  obviously  such  paraffin  is  not  to  be 
considered  as  a  normal  constituent  of  the  explosive,  and  care  should 
also  be  taken  in  unwrapping  the  cartridge  to  prevent  scales  and 
flakes  of  paraffin  from  becoming  mixed  with  the  sample. 

The  best  method  of  sampling  consists  in  opening  the  wrapper  of 
each  cartridge,  spreading  it  out  and  cutting  off  from  3  to  5  cm.  from 
each  end  of  the  roll  of  explosive  thus  exposed.  These  ends  are 
rejected  and  the  remainder  carefully  broken  up  to  form  a  homoge- 
neous mass.  When  a  sample  representing  a  large  quantity  of  pow- 
der— for  example,  a  day's  <  utput  of  a  factory — is  to  be  prepared,  a 
number  of  cartridges  are  taken  fr^m  different  mixings,  the  central 
portions  of  each  cartridge  are  selected  in  the  manner  described,  and 
these  portions  are  finely  broken  up  in  a  large  porcelain  evaporating 
dish  or  on  a  sheet  of  paraffined  paper.  The  mass  is  carefully  stirred 
with  a  clean  spatula,  or  is  rolled  from  side  t"  side  upon  the  paraffined 
paper  in  the  manner  usually  followed  in  preparing  a  sample  of  ore 
for  assay.  The  stirring  of  the  sample,  or  its  rolling  back  and  forth 
upon  the  paraffined  paper,  should  occupy  not  less  than  five  minutes, 
and  the  best  results  are  obtained  from  such  sampling  when  the 
explosive  has  been  previously  broken  up  to  as  fine  a  meal  as  possible 
by  crumbling  in  the  fingers  or  by  gentle  pressure  with  the  spatula. 
A  spatula  suitable  for  this  purpose  is  made  of  horn,  or  of  wood 
saturated  with  paraffin  so  that  it  will  not  absorb  nitroglycerin. 

From  the  large  sample  prepared  as  described  a  sample  of  50  to 
100  grams  is  taken  by  selecting  small  portions  from  different  parts 


14 


ANALYSIS   OF   BLACK   POWDER  AND   DYNAMITE. 


of  the  mixed  material,  mixing  these  portions,  and  placing  the  mix- 
ture in  the  sample  bottle. 

In  preparing  a  sample  of  dynamite  there  are  several  factors  that 
must  be  constantly  borne  in  mind.  If  a  thoroughly  mixed  sample 
is  prepared  and  allowed  to  remain  for  some  time  in  a  sample  bottle, 
a  segregation  occurs,  and  the  lower  portions  of  the  material  in  the 
sample  bottle  become  richer  in  nitroglycerin  at  the  expense  of  the 
upper  portions.  In  some  dynamites,  particularly  one  that  contains 
almost  as  much  nitroglycerin  as  its  absorbent  base  can  hold,  this 
change  occurs  rapidly,  and  may  make  a  difference  of  several  per  cent 
in  a  few  days.  The  tendency  to  segregate  is  greatest  in  a  tah1  bottle, 
and  is  favored  by  warmth,  the  action  taking  place  several  times  as 
rapidly  at  30°  C.  as  at  20°  C.  An  indication  of  the  amount  of  segre- 
gation that  is  possible  hi  dynamite  is  seen  from  the  results  of  the  fol- 
lowing experiment : 

A  sample  of  dynamite  was  prepared  by  carefully  breaking  up  and 
sampling  two  sticks  of  60  per  cent  dynamite,  about  300  grams  being 
taken  and  placed  in  an  ordinary  bottle  of  250  c.  c.  capacity  (diameter 
about  6  cm.,  height  about  14  cm.).  At  the  time  the  sample  was 
placed  in  the  bottle  the  analysis  of  the  material  gave  the  following 
results : 

Analysis  of  60  per  cent  dynamite. 


[W.  C.  Cope,  analyst.) 


Per  cent. 
1.40 


Moisture 

Nitroglycerin 60.  60 

Potassium  nitrate 18.  64 

Calcium  carbonate 1.  25 

Wood  pulp 18.11 

At  the  end  of  10  days'  exposure  to  a  temperature  of  32°  to  33°  C. 
(average,  32.5°  C.)  samples  were  taken  from  the  top,  middle,  and 
bottom  of  the  material  hi  the  bottle,  and  the  following  results  were 
obtained : 

Analyses  of  different  parts  of  exposed  sample  of  60  per  cent  dynamite. 
[W.  C.  Cope,  analyst.] 


Constituents. 

Sample 
from  top. 

Sample 
from 
middle. 

Sample 
from 
bottom. 

Moisture  

Per  cent. 
1  25 

Per  cent. 
1  16 

Per  cent. 
1  17 

Nitroplvcerin  

59  46 

60  55 

62  86 

Potassium  nitrate  

19  91 

18  44 

17  42 

Calcium  carbonate  

1  37 

1  33 

1  26 

Wood  pulp  

18  01 

18  52 

17  2Q 

DYNAMITE.  15 

Another  experiment  was  made  to  illustrate  segregation  in  cartridges 
themselves. 

Whole  cartridges  of  40  per  cent,  45  per  cent,  and  60  per  cent  dyna- 
mite were  placed  upright  (on  end)  in  a  constant-temperature  oven  at 
40°  for  a  period  of  four  weeks,  the  cartridges  being  supported  by 
small  wire  tripods  within  glass  cylinders.  Pinholes  were  punched  in 
the  bottom  of  the  wrappers  to  allow  the  escape  of  any  accumulation 
of  nitroglycerin,  but  no  such  leakage  occurred. 

At  the  end  of  four  weeks  samples  were  taken  from  the  top  and 
bottom  of  each  cartridge,  each  sample  representing  about  a  2-inch 
length  of  cartridge.  The  following  results  of  analyses  of  these 
samples  show  the  segregation  of  the  nitroglycerin : 

Analyses  of  parts  of  samples  of  dynamite  left  standing  on  end  for  four  weeks  at  40°  C. 

[J.  H.  Hunter,  analyst.] 


Grade  of  dynamite, 

40 

45 

60 

Part  of  cartridge  sampled. 

Nitroglycerin. 

Per  cent. 
38.20 
40.96 

Per  cent. 
45.07 
47.98 

Per  cent. 
57.27 
63.26 

From  the  above  described  experiments  it  will  be  seen  that  the 
sampling  of  dynamite  involves  problems  not  met  in  the  preparation 
of  ore  for  assay. 

To  determine  any  possible  segregation  due  to  nitroglycerin  adhering 
to  the  dish  in  which  a  sample  is  mixed,  500  grams  of  dynamite  was 
mixed  in  a  large  evaporating  dish,  and,  when  thorough  mixing  had 
been  effected,  was  poured  on  a  piece  of  paraffined  paper.  An  analy- 
sis was  then  made  of  the  large  sample  upon  the  paraffined  paper,  and 
the  material  adhering  to  the  sides  of  the  evaporating  dish  was 
removed  by  means  of  ether  and  analyzed.  It  was  found  that  there 
was  little  difference  between  the  composition  of  the  two  samples.  It 
has  been  suggested  that  considerable  changes  in  the  moisture  content 
of  dynamite  can  occur  during  sampling,  but  this  opinion  does  not  seem 
correct.  In  the  factory  dynamite  is  usually  mixed  in  an  open  mixer 
exposed  to  the  atmosphere;  consequently  the  percentage  of  moisture 
taken  up  or  lost  in  the  short  length  of  time  that  the  explosive  is 
exposed  to  the  air  during  sampling  should  be  proportional  only  to 
the  difference  between  the  hygrometric  condition  of  the  air  at  the 
time  the  dynamite  was  made  and  that  at  the  time  it  was  sampled. 
To  investigate  this  question  further  an  experiment  was  made  as 
follows : 

Two  cartridges  of  one-half  pound  (226  grams)  each  were  mixed 
together  quickly,  and  with  as  little  exposure  to  the  air  as  possible. 
This  original  sample  was  found  to  contain  1.10  per  cent  moisture. 


16  ANALYSIS   OF   BLACK   POWDER  AND   DYNAMITE. 

A  100-gram  portion  of  this  large  sample  was  then  mixed  on  a  large 
watch  glass  for  10  minutes  on  a  damp  day  when  the  humidity  of 
the  air  as  determined  by  hygrometer  readings  was  75  per  cent. 
Another  100-gram  portion  was  similarly  treated  on  a  dry  day  when 
the  humidity  was  only  19  per  cent.  Determinations  of  moisture 
were  then  made  on  these  two  portions  with  the  following  results: 

Effect  of  exposure  during  sampling  on  moisture  content  of  dynamite. 

Treatment  of  sample.  Moisture. 

Per  cent. 

Without  undue  exposure 1. 10 

Stirred  10  minutes  in  moist  atmosphere 1. 25 

Stirred  10  minutes  in  dry  atmosphere 1. 10 

From  these  results  it  will  be  seen  that  the  condition  of  the  atmos- 
phere has  little  effect  on  the  moisture  content  of  a  sample  when  the 
sampling  is  done  with  reasonable  dispatch  and  when  atmospheric 
conditions  are  not  abnormal. 

CHEMICAL  EXAMINATION. 
QUALITATIVE    EXAMINATION. 

When  no  information  is  available  as  to  the  class  to  which  an  explo- 
sive to  be  analyzed  belongs,  a  complete  qualitative  analysis  is  desir- 
able, so  that  the  proper  methods  of  quantitative  separation  may  be 
followed. 

For  the  qualitative  examination  of  a  dynamite  of  any  type  a  sam- 
ple of  20  to  25  grams  is  most  convenient.  The  sample  is  placed  in  a 
1-inch  test  tube,  which  is  then  filled  to  about  two-thirds  of  its  depth 
with  ether,  stoppered,  and  well  shaken.  The  ether  is  decanted 
through  a  filter  paper  and  fresh  ether  is  added  to  the  tube.  This 
treatment  is  repeated  several  times,  and  the  residue  is  finally  trans- 
ferred to  the  filter  and  again  washed  with  fresh  ether.  After  the 
ether  is  drained  off,  the  filter  paper  with  its  contents  is  removed 
from  the  funnel,  spread  out  on  a  glass  plate,  and  placed  in  a  drying 
oven  for  a  short  time  until  nearly  all  the  ether  has  evaporated.  The 
dry  residue  is  transferred  from  the  filter  back  to  the  test  tube,  and  is 
then  ready  for  treatment  with  cold  water,  to  remove  the  water- 
soluble  constituents. 

The  ether  solution  is  evaporated  on  a  steam  bath  or  electric  heater 
at  a  low  temperature  until  all  odor  of  ether  has  disappeared.  If 
the  evaporation  has  caused  the  deposition  of  water  in  the  beaker 
with  the  extract,  this  water  is  removed  by  placing  the  beaker  in  a 
vacuum  desiccator  for  an  hour  or  two.  The  presence  of  nitro- 
glycerin  is  readily  noted,  the  characteristic  oily  appearance  of 


DYNAMITE.  17 

nitroglycerin  and  its  viscosity  serving  to  identify  it.  A  convenient 
chemical  test  is  to  mix  a  drop  of  the  heavy  liquid,  supposed  to  be 
nitroglycerin,  with  1  or  2  c.  c.  of  concentrated  sulphuric  acid  in  a 
test  tube,  and  then  to  add  about  1  c.  c.  of  mercury.  No  stopper  of 
any  sort  should  be  placed  in  the  tube,  but  it  should  be  shaken  quickly 
from  side  to  side  so  as  to  cause  intimate  contact  of  the  mercury  with 
the  acid  mixture.  For  1  or  2  minutes  little  effect  will  be  observed, 
but  after  a  short  time  there  will  be  noted,  if  the  material  under 
examination  is  nitroglycerin,  the  evolution  of  bubbles  of  gas  from 
the  liquid  at  the  point  where  it  comes  in  contact  with  the  mercury, 
and  the  characteristic  smell  of  nitrogen  oxides  will  be  noted.  The 
nitric  oxide  (NO)  produced  is  colorless,  but  upon  coming  in  con- 
tact with  the  air  it  turns  red  or  reddish-brown,  forming  nitrogen 
peroxide  (NO2).  A  simpler  test  for  the  presence  of  nitroglycerin, 
though  by  no  means  so  satisfactory  as  the  one  just  described,  con- 
sists in  taking  up  a  small  amount  of  the  liquid  in  a  capillary  glass 
tube,  and  holding  it  cautiously  in  a  flame.  A  strong  detonation 
will  result  if  the  liquid  is  nitroglycerin.  It  is  of  course  evident  that 
there  should  be  not  more  than  a  tiny  fraction  of  a  drop  of  nitro- 
glycerin used  in  such  a  test,  the  best  results  being  obtained  when 
a  very  thin  and  small  capillary  is  used,  containing  not  more  than 
0.01  of  a  drop  of  the  liquid  tested. 

If  sulphur  is  present  in  the  ether  extract  it  will  crystalize  in  needles 
or  small  granular  masses  in  the  residue  upon  the  evaporation  of  the 
ether.  The  crystals  of  sulphur  can  be  removed,  washed  free  from 
nitroglycerin  with  a  little  acetic  acid  (70  per  cent  or  glacial),  after 
which  they  should  be  washed  with  water,  dried,  and  heated  over  a 
flame.  The  odor  of  sulphur  dioxide  (SO2)  will  identify  the  crystals 
as  sulphur.  Trinitrotoluene  appears  as  long  yellowish  needles, 
which  may  be  recrystallized  from  alcohol  and  identified  by  their 
melting  point  (80°  C.),  or  by  the  color  test  with  potassium  or  sodium 
hydroxide.0  This  color  test  is  valuable  as  a  means  of  identifying 
many  of  the  nitrosubstitution  products,  although  in  a  mixture  the 
color  produced  by  one  constituent  may  completely  hide  the  others. 
For  example,  the  wine-red  color  obtained  from  trinitrotoluene  may 
prevent  the  identification  of  other  nitrocompounds  that  maybe 
present.  The  test  may  be  made  directly  on  a  portion  of  the  ether 
extract,  since  the  presence  of  nitroglycerin  does  not  in  any  way 
interfere.  The  sample  under  examination  is  dissolved  in  2  to  3  c.  c. 
of  acetone  or  methyl  alcohol,  and  a  few  drops  of  10  per  cent  potas- 
sium or  sodium  hydroxide  added.  The  characteristic  colors  pro- 
duced by  various  nitrosubstitution  compounds  are  shown  in  the 
table  following. 

«  Gody,  L.,  Traite  thdorique  et  pratique  des  matures  explosives,  1907,  p.  599. 
67709°— Bull.  51—13 2 


18 


ANALYSIS   OF   BLACK   POWDEK   AND  DYNAMITE. 

Color  reactions  of  nitrosubstitution  products  with  alkalies. 


Substance. 

Form. 

Color  of  solution. 

Result  of  addition  of  alkaline 
solution. 

Liquid 

Colorless  

No  effect. 

Dinitrobenzene                

Crystal  

Faint  yellow  

Purple-rose,  turning  to  deep 

Trinitrobenzene  

do  

Colorless   to   pale 

claret. 
Rich  purple-brown. 

Mononitrotoluene  (ortho) 

Liquid 

yellow, 
do     

No  effect. 

Crystal 

do 

Slight  yellow 

Mononitrotoluene  (para) 

do 

....  do    

No  effect. 

do 

do       .... 

Gradual  evolution  of  azure 

Trinitrotoluene 

do 

do 

blue  on  standing. 
Deep  wine-red  brown. 

Mononitronaphthalene    

do    

do  

No  effect. 

Dinitronaphthalene 

do 

Pale  yellow 

Reddish-yellow. 

Trinitronaphthalene  

...do  

...do.... 

Bright  scarlet. 

Tetranitronaphthalene       

do 

.do  

Reddish-yellow. 

do 

Golden-yellow 

Precipitate    of    crystals    of 

potassium  picrate'  (orange). 

Rosin,  vaseline,  paraffin,  oils,  etc.,  are  found  in  the  extract,  after 
evaporation  of  the  ether,  as  a  dark-colored,  greas}^  mass  on  the  sur- 
face of  the  nitroglycerin  or  adhering  to  the  walls  of  the  beaker. 
Small  amounts  of  resins  and  oils  are  generally  found  in  the  extracts 
from  ordinary  dynamite,  these  being  normal  constituents  of  the 
wood  pulp,  flour,  or  similar  absorbents.  The  amount  of  such  mate- 
rials present  is  usually  too  small  to  be  of  any  importance,  and  where 
only  small  traces  are  found  they  may  best  be  disregarded.  If  it  is 
desired  to  identify  such  materials  the  method  for  quantitative 
determination  described  later  may  be  followed. 

The  water  solution  is  examined  for  sodium,  potassium,  ammonium, 
zinc,  the  nitrate  ion,  etc.  The  qualitative  and  quantitative  tests  for 
these  elements  are  discussed  fully  in  all  textbooks  of  analysis,  and 
accordingly  need  not  be  repeated  here.  In  ordinary  qualitative 
work  the  writers  have  found  the  ring  test  for  nitrates,  with  the  use 
of  the  nitrometer  in  any  doubtful  case,  to  be  most  satisfactory; 
potassium  and  sodium  are  best  identified  by  the  color  they  impart 
to  the  flame  of  the  Bunsen  burner,  viewed  through  at  least  two 
thicknesses  of  cobalt  glass.  The  best  test  for  ammonium  is  the 
evolution  of  ammonia  by  reaction  with  calcium  oxide  or  sodium 
hydroxide.  Small  quantities  of  iron,  aluminum,  chlorides,  sul- 
phates, etc.,  are  generally  found  in  all  dynamites  as  impurities  from 
the  raw  materials  used. 

The  residue  insoluble  in  water  is  treated  with  cold  dilute  hydro- 
chloric acid;  effervescence,  if  noted,  is  an  indication  of  the  presence 
of  a  carbonate,  and  the  usual  tests  are  then  made  for  CO2.  The  acid 
extract  after  filtering  is  tested  for  calcium,  magnesium,  zinc,  etc., 
whose  carbonates  or  oxides  may  have  been  present  in  the  powder  as 
antacids. 

The  residue  insoluble  in  water  and  dilute  acid  is  best  examined 
under  the  microscope,  a  magnification  of  30  to  50  diameters  being 


DYNAMITE.  19 

most  convenient  for  all  ordinary  work.  The  identification  of  starch, 
cereal  products,  wood  pulp,  sawdust,  kieselguhr,  nitrocellulose,  etc.,  is 
discussed  in  another  part  of  this  paper. 

A  starch  test  is  readily  made  by  heating  a  portion  of  the  mate- 
rial to  boiling  with  dilute  acid,  cooling  and  adding  a  drop  of  iodine 
solution,  this  operation  producing  an  intense  blue  coloration  if 
starch  is  present. 

DETERMINATION    OF   MOISTURE. 

The  moisture  present  in  dynamite  may  be  determined  in  the  fol- 
lowing ways: 

(a)  By  drying  in  a  desiccator  over  sulphuric  acid,  calcium  chloride, 
or  other  suitable  drying  agent  without  vacuum. 

(b)  By  drying  in  a  desiccator  with  vacuum. 

(c)  By  passing  dry  air  through  the  sample. 

These  methods  have  been  carefully  studied,  and  the  first  method, 
dry-ing  over  sulphuric  acid  in  a  desiccator,  has  been  found  to  have 
the  widest  application,  and  to  be  the  most  desirable  in  the  analysis 
of  explosives.  In  the  determination  of  moisture  in  a  sample  of 
dynamite  a  number  of  important  factors  should  be  considered  in 
order  that  accurate  results  may  be  obtained.  The  weight  of  the 
sample,  the  manner  in  which  the  sample  is  spread  upon  the  watch 
glass,  the  size  and  type  of  desiccator,  the  exposed  area  of  the  desic- 
cating agent,  as  well  as  its  quantity  and  condition  and  the  tem- 
perature at  which  the  desiccation  is  carried  out — all  have  an  important 
bearing  on  the  loss  of  wreight  resulting  from  desiccation,  and  unless 
care  is  taken  moisture  determinations  made  at  different  .times  on  the 
same  sample  of  dynamite  will  frequently  give  somewhat  different 
results,  oWing  to  the  slight  variations  in  some  of  the  above-named 
factors. 

Preliminary  studies  were  made  to  determine  the  amount  of  dyna- 
mite that  is  most  suitable  for  the  determination  of  moisture,  and  the 
thickness  with  which  the  sample  should  be  spread  upon  the  watch 
glass.  The  results  of  these  tests  showed  that  a  sample  of  less  than 
2  grams  of  explosive  is  unsatisfactory,  owing  to  the  errors  intro- 
duced, for  example,  by  particles  of  material  being  carried  away  by 
the  air  during  weighing,  or  upon  opening  the  desiccator.  When 
more  than  2  grams  of  sample  was  taken  the  length  of  time  required 
to  effect  thorough  drying  was  unduly  long;  and  consequently  2 
grams  of  material,  spread  evenly  on  the  concave  surface  of  a  3-inch 
watch  glass,  was  deemed  the  best  amount  for  the  determination. 
\Vhen  only  one  or  two  analyses  have  to  be  run  at  a  time,  it  is  con- 
venient to  use  a  separate  5  or  6  inch  desiccator  for  each  sample,  the 
bottom  of  the  desiccator  containing  about  50  to  75  c.  c.  of  concen- 
trated sulphuric  acid,  and  the  watch  glass  being  held  by  a  triangle 


20  ANALYSIS   OF   BLACK   POWDEB  AND   DYNAMITE. 

at  a  convenient  and  suitable  distance  above  the  acid.  Objections 
have  been  raised  a  to  the  use  of  sulphuric  acid  as  a  desiccating  agent 
in  the  determination  of  moisture  in  dynamite.  The  experience  of 
the  writers  has  shown  these  objections  to  be  without  grounds. 

When  a  number  of  determinations  are  being  made  at  the  same 
time  it  is  convenient  to  use  larger  desiccators,  and  the  10-inch  size  has 
been  found  to  be  satisfactory,  five  watch  glasses  being  conveniently 
held  at  one  tune  in  such  a  desiccator. 


IN   ORDINARY    DESICCATORS. 


The  period  required  for  desiccation  of  a  sample  of  dynamite  in 
an  ordinary  desiccator  is  about  3  days  or  72  hours.  The  first  12 
hours  within  the  desiccator  reduces  the  moisture  content  to  a  very 
low  percentage,  but  it  has  been  found  desirable  to  allow  all  samples 
to  remain  a  further  period  of  60  hours,  as  the  remainder  of  the  moisture 
is  slowly  removed.  The  loss  in  weight,  at  the  end  of  three  days, 
of  the  2-gram  sample  of  dynamite  on  the  watch  glass  is  taken  as 
moisture.  After  three  days7  drying,  small  amounts  of  moisture  are 
still  present,  particularly  in  the  wood  pulp,  but  drying  longer  than 
three  days  has  not  been  found  desirable  in  ordinary  analytical  work. 
By  long-continued  desiccation,  over  either  calcium  chloride  or 
sulphuric  acid,  a  further  gradual  loss  occurs  which  is  evidently  due 
to  volatilization  of  nitroglycerin,  and  the  amount  of  this  loss  varies 
with  the  temperature.  Taking  the  loss  of  weight  at  the  end  of  three 
days  as  representing  moisture  has  been  found  to  give  uniform  results 
in  the  case  of  dynamites  of  most  varied  composition,  and  has 
been  adopted  in  the  bureau's  laboratory  as  a  standard  method, 
although  it  is  impossible  to  say  that  at  the  end  of  any  definite  time 
all  moisture  has  been  removed  from  the  sample  and  that  fflrther  loss 
is  due  to  volatilization  of  nitroglycerin. 

Care  should  always  be  taken  to  spread  the  sample  in  a  thin  and 
uniform  layer  over  nearly  the  entire  surface  of  the  watch  glass,  and 
the  spreading  should  be  done  as  quickly  as  possible  to  prevent 
undue  exposure  to  the  atmosphere.  Experiments  in  which  different 
sizes  of  desiccators  (4-inch  to  9-inch)  were  used  showed  that  the  rate 
of  drying  increased  as  the  ratio  of  acid  surface  to  powder  surface 
increased,  but  that  in  three  days  the  loss  in  all  cases  was  practically 
the  same.  The  effect  of  such  variation  is  shown  in  the  following 
table  of  results  of  tests  of  explosives  containing  amounts  of  moisture 
greater  than  that  in  ordinary  dynamite.  The  table  also  shows  a 
comparison  between  the  efficiencies  of  two  types  of  desiccators — 
the  Scheibler,  or  ordinary  type,  which  contains  the  acid  in  the  bot- 

a  Gody,  L.,  Traite  ttuSorique  et  pratique  des  matures  explosives,  1907,  p.  382;  Guttmann,  O.,  Schiess- 
und  Sprengmittel,  1900,  p.  162. 


DYNAMITE. 


21 


torn  below  the  sample,  and  the  Hempel  type  in  which  the  acid  'is 
contained  in  the  top  or  cover,  above  the  sample.  With  an  acid  sur- 
face about  75  per  cent  as  great  as  in  the  ordinary  type  the  Hempel 
desiccator  appears  to  be  slightly  more  efficient  than  the  Scheibler. 

Results  of  moisture  determinations  shoiving  effect  of  variation  in  acid  surface  and 

in  type  of  desiccator. 


Scheibler. 

Scheibler. 

Hempel. 

Size  of  desiccator  

4-inch. 

9-inch. 

6-inch, 

j  7  square 
(  inches. 

50  square 
inches. 

38  square 
inches. 

Name  of  explosive. 

Time  of 
drying. 

Moisture  content  determined  by 
loss  of  weight. 

Explosive  A*..   .           

Hours. 
6 
12 
24 
48 
72 
2 
5 
24 
48 
72 

Percent. 
5.73 
8.82 
10.06 
10.52 
10.66 
1.89 
4.09 
5.34 
5.49 
5.50 

Percent. 
9.84 
10.11 
10.33 
10.63 
10.68 

Per  cent. 
9.97 
10.29 
10.43 
10.65 
10.79 
3.18 
4.88 
5.51 
5.60 
£63 

5.50 

5.59 

a  Arbitrary  designation  of  sample. 

The  quantity  of  acid  used  in  the  desiccator  must  also  be  considered, 
because  the  dilution  of  the  acid  by  the  absorbed  moisture  is  dependent 
upon  the  amount  of  acid  present.  In  general,  the  acid  contained  in  a 
desiccator  does  not  require  frequent  renewal,  and  when  from  50  to  75 
c.  c.  of  concentrated  sulphuric  acid  (H2SO4)  is  used  in  the  desiccator 
the  renewal  of  this  material  once  each  month  or  once  every  two 
months  is  all  that  is  necessary. 

The  following  experiment  illustrates  the  effect  of  dilution  of  the 
sulphuric  acid  by  the  absorption  of  considerable  moisture  from  pow- 
der samples.  Two  samples  of  the  same  dynamite  were  desiccated  in 
similar  desiccators,  one  containing  75  c.  c.  of  96  per  cent  sulphuric 
acid,  the  other  the  same  volume  of  90  per  cent  sulphuric  acid.  In 
three  days  the  losses  of  moisture  were  1.10  per  cent  and  1.02  per 
cent  respectively,  and  in  five  days  1.17  per  cent  and  1.05  per  cent, 
respectively.  In  order  that  75  c.  c.  of  96  per  cent  acid  could  become 
diluted  to  90  per  cent  by  the  absorption  of  moisture  from  dynamite 
samples  it  would  be  necessary  that  all  of  the  moisture  from  about 
460  2-gram  samples  of  dynamite,  each  containing  1  per  cent  mois- 
ture, be  absorbed  by  the  acid.  It  is  therefore  obvious  that  the  acid 
in  the  desiccators  will  not  become  diluted  enough  in  one  or  two 
months  to  lose  appreciably  its  affinity  for  moisture. 


22 


ANALYSIS   OF   BLACK   POWDEE   AND   DYNAMITE. 


The  effect  of  temperature  on  the  moisture  determination  is  shown 
in  the  following  experiments,  made  with  a  60  per  cent  dynamite. 
Three  determinations  of  moisture  were  made  on  the  same  sample  at 
widely  different  temperatures.  Two  grams  of  the  sample  in  one 
desiccator  were  placed  in  an  incubator,  the  temperature  of  which, 
by  means  of  a  thermostat,  was  regulated  to  a  range  of  36°  to  38°  C. 
(96.8°  to  100.4°  F.).  A  second  desiccator  containing  another  2 
grams  of  the  sample  was  placed  out  of  doors,  the  temperature  varying 
during  the  experiment  from  -23°  to  2°  C.  (-9.4°  to  35.6°  F.).  A 
third  desiccator  containing  a  third  2-gram  portion  of  the  sample  was 
left  at  room  temperature,  which  varied  from  17°  to  25°  C.  (63°  to  77° 
F.).  In  each  of  these  experiments  the  2-gram  parts  of  the  sample 
were  spread  upon  3-inch  watch  glasses,  each  watch  glass  being  placed 
in  a  separate  4-inch  desiccator  containing  75  c.  c.  of  fresh  sulphuric 
acid.  The  results  are  tabulated  below: 

Results  of  tests  to  determine  the  moisture  content  of  dynamite,  showing  the  influence  of 

temperature. 


1 

2 

3 

4 

5 

6 

Temperature. 

Loss  of 

Ether  extract. 

Sample 
No 

Maxi- 
mum. 

Mini- 
mum. 

Mean. 

Days, 
exposed. 

weight 
on  des- 
iccation. 

By  loss. 

By  direct 
weight. 

.Nitroglycerin  in 
ether  extract.** 

°C. 

°C. 

°<7. 

Per  cent. 

Grams. 

Grams. 

Grams. 

Per  cent. 

3 

1.00 

6 

1.06 

1 

25 

17 

21 

7 

1.06 

10 

1.19 

13 

1.31 

1.  2158 

1.2126 

1.2051 

60.26 

3 

1.69 

6 

2.49 

2 

38 

36 

37 

n 

2.74 

10 

3.54 

13 

4.12 

1.1563 

1.  1522 

1.  1397 

56.99 

-7 

-16 

1' 

3 

0.60 

—3 

—23 

6 

3 

0 

-14 

-9 

7 

0.72 

2 

g 

10 

0.67 

20 

18 

19 

I           13 

1.03 

1.2243 

1.  2220 

1.  2114 

60.57 

o  Determined  by  nitrometer. 

After  the  weighings  had  been  made  on  the  thirteenth  day  the 
samples  were  carefully  transferred  to  Gooch  crucibles,  and  extracted 
with  ether  in  a  Wiley  extractor."  The  crucibles  were  then  dried  at  100° 
C.,  and  the  losses  in  weight  determined,  which  are  given  in  column  5. 
The  nitroglycerin  in  each  sample  of  ether  extract  was  then  deter- 
mined by  the  nitrometer  after  the  ether  had  been  evaporated  (see 
p.  35).  The  results  shown  under  "loss  of  weight  by  desiccation " 
(column  4)  indicate  the  pronounced  influence  which  temperature  has 
on  the  determination  of  moisture.  In  the  case  of  sample  2  most  of 
the  moisture  was  probably  lost  within  the  first  24  hours,  the  further 


For  the  method  used  in  the  extraction  see  p. 


DYNAMITE. 


23 


loss  being  entirely  due  to  the  evaporation  of  nitroglycerin.  In  the 
case  of  the  sample  3  the  weight  first  taken,  at  the  end  of  three  days, 
showed  a  loss  of  only  0.60  per  cent.  As  previous  experiments  had 
shown  that  this  amount  of  moisture  can  be  removed  from  60  per 
cent  dynamite  by  about  two  hours'  desiccation,  it  is  probable  that 
the  loss  noted  during  the  first  three  days  resulted  during  the  first 
two  hours'  desiccation,  before  the  sample  became  frozen.  Practi- 
cally no  further  loss  occurred  in  this  sample  up  to  10  days,  and  the  loss 
which  occurred  between  the  tenth  and  thirteenth  day  was  due  to  the 
fact  that  the  sample  had  thawed.  As  the  temperature  in  the  labora- 
tory frequently  reaches  35°  C.  or  more  during  the  summer,  it  is 
evident  that  abnormally  high  results  sometimes  obtained  during 


FIGURE  1.— Influence  of  temperature  on  determination  of  moisture  in  60  per  cent  dynamite  by  desiccation 
over  sulphuric  acid.    Temperature  (mean):  No.  1, 21°  C.;  No.  2, 37°  C.;  No.  3,  —9°  C. 

warm  days  of  summer  may  be  in  error  to  a  considerable  extent,  being 
only  in  part  due  to  loss  of  moisture  and  in  part  to  volatilization  of 
nitroglycerin.  Since  incorrect  results  are  obtained  when  moisture 
is  determined  at  a  low  temperature,  no  determinations  of  moisture 
should  be  made  at  a  temperature  sufficiently  low  to  cause  the  sample 
to  freeze.  In  order  that  perfectly  uniform  results  may  be  obtained 
with  samples  of  dynamite,  the  temperature  of  the  room  in  which  the 
desiccation  is  carried  out  should  be  practically  constant  at  20°  C. 
This  is  a  normal  working  temperature,  and  when  moisture  deter- 
minations are  made  at  temperatures  materially  above  or  below  it, 
allowance  should  be  made  for  the  influence  of  the  abnormal  tempera- 
ture. The  results  given  in  the  table  on  p.  22  are  shown  in  the  form 
of  curves  in  figure  1.  The  curve  for  sample  3  represents  the  results 


ANALYSIS  OF  BLACK  POWDER  AiSTD 


of   the  first   10  days'   exposure,   during  which   period   the  sample 
remained  frozen. 

In  the  determination  of  moisture  by  the  bureau's  explosives  labo- 
ratory, sulphuric  acid  has  been  accepted  as  the  standard  desiccating 
agent.  As  many  chemists  prefer  to  use  calcium  chloride,  the  following 
experiment  is  of  interest,  as  showing  the  difference  in  efficiency  of 
these  two  desiccating  agents.  Six  2-gram  samples  of  60  per  cent 
dynamite  were  weighed  from  a  large,  well-mixed  sample.  Three  of 
these  samples  were  desiccated  over  calcium  chloride  and  three  over 
sulphuric  acid.  An  individual  6-inch  Scheibler  desiccator  was  used 
for  each  sample.  Weighings  made  at  intervals  showed  the  loss  of 
moisture  as  follows: 

Results  of  desiccation   of  60  per  cent  dynamite  over  calcium  chloride   and  over  sul- 
phuric acid,  at  room  temperature. 


Time. 

Designa- 
tion of 
sample. 

Loss  of 
weight  over 
calcium 
chloride. 

Designa- 
tion of 
sample. 

Loss  of 
weight  over 
sulphuric 
acid. 

Days. 

Per  cent. 

Per  cent. 

A 

A 

0.50 

C 

0.64 

A 

A 

.59 

C 

.73 

I 

A 

62 

C 

.79 

I 

B 

.66 

D 

.87 

1 

A 

.67 

C 

.84 

2 

B 

.77 

D 

.94 

3 

A 

.77 

C 

.96 

3 

B 

.80 

D 

.97 

3 

E 

.84 

F 

1.02 

5 

A 

.84 

C 

1.01 

5 

B 

.87 

D 

1.01 

5 

E 

.91 

F 

1.07 

6 

A 

.84 

C 

1.02 

6 

A 

.87 

D 

1.05 

6 

E 

.93 

F 

1.10 

10 

A 

.95 

C 

1.11 

10 

B 

1.00 

D 

1.17 

10 

E 

1.00 

F 

1.20 

13 

A 

1.07 

C 

1.23 

13 

B 

1.10 

D 

1.32 

13 

E 

1.15 

F 

1.36 

16 

A 

1.16 

C 

1.33 

16 

B 

1.13 

D 

1.46 

16 

E 

1.25 

F 

1.48 

19 

E 

1.25 

F 

1.53 

20 

E 

1.37 

F 

1.60 

34 

E 

1.72 

F 

2.01 

50 

E 

2.22 

F 

2.55 

75 

E 

2.82 

F 

3.35 

111 

E 

3.67 

F 

4.55 

183 

E 

5.77 

F 

7.55 

237 

E 

6.85 

F 

9.20 

These  results,  plotted  in  the  form  of  curves  for  the  two  samples 
E  and  F,  upon  which  desiccation  was  continued  the  longest,  are 
shown  in  figure  2. 

The  fact  that  nitroglycerui  is  more  or  less  volatile  even  at  ordinary 
temperatures  is  recognized  by  most  explosives  chemists,  and  in 
some  laboratories  an  endeavor  is  made  to  avoid  loss  of  nitrogly- 
cerui during  desiccation  by  keeping  the  atmosphere  within  the 
desiccator  saturated  with  nitroglycerin  vapors.  This  is  done  by 
placing  in  the  desiccator,  together  with  the  sample  of  dynamite  on 


m  X  A  MITE. 


wliich  moisture  is  to  be  determined,  a  quantity  of  nitroglycerin  on 
a  watch  glass,  it  being  assumed  that  the  evaporation  of  this  nitro- 
glycerin will  saturate  the  atmosphere  in  the  desiccator  and  minimize 
tlu»  loss  of  nitroglycerin  from  the  sample  of  dynamite. 

To  test  the  value  of  such  method  the  following  experiments  were 
made:  Four  samples  (2  grams  each)  of  the  same  60  per  cent  dyna- 


12 


24 


36 


48 


60 
DAYS 


84 


96 


108 


120 


FIGURE  2.—  Results  of  desiccation  of  60  per  cent  dynamite  over  calcium  chloride  (E)  and  over  sulphuric 

acid  (F)  at  room  temperature. 

mite  used  above  were  spread  on  3-inch  watch  glasses  and  placed  hi 
separate  desiccators.  Directly  underneath  each  of  the  watch  glasses 
was  placed  a  watch  glass  containing  a  layer  of  fine  dry  sand  saturated 
with  nitroglycerin.  Two  of  the  desiccators  contained  sulphuric  acid 
and  two  calcium  chloride.  Weighings  of  the  dynamite  samples  at 
intervals  showed  losses  of  weight  as  follows: 

Results  of  desiccation  of  60  per  cent  dynamite  over  calcium  chloride  and  over  sulphuric 
acid  in  an  atmosphere  saturated  with  nitroglycerin  vapors. 


Designa- 
tion of 
sample. 

Desiccation  over  cal- 
cium chloride. 

Designa- 
tion of 
sample. 

Desiccation  over  sul- 
phuric acid. 

Time. 

Loss  of 
weight. 

Time. 

Loss  of 
weight. 

A 

B 

A 

B 
A 
B 
A 
B 
A 
B 

Days. 

3 
6 
6 
10 
10 
13 
13 
19 
19 

Percent. 
0.77 
.80 
.93 
.97 
1.02 
1.00 
1.15 
1.17 
1.25 
1.35 

C 
D 
C 
D 
C 
D 
C 
D 
C 
D 

Day*. 
3 
3 
6 
6 
10 
10 
13 
13 
19 
19 

Percent. 

0.92 
.10 
.12 
.13 
.15 
.20 
.25 
.31 
.40 

26 


ANALYSIS   OF   BLACK   POWDER  AND   DYNAMITE. 


Comparing  these  results  with  those  of  the  table  on  page  24,  it  will 
be  noted  that  the  placing  of  an  additional  amount  of  nitroglycerin 
in  the  desiccator  with  the  sample  of  dynamite  has  practically  no 
effect  on  the  amount  of  nitroglycerin  lost  from  the  sample. 

The  fact  that  nitroglycerin  volatilizes  in  the  desiccator  in  the 
presence  of  either  sulphuric  acid  or  calcium  chloride  suggested  the 
carrying  out  of  experiments  to  determine  whether  a  sample  of  dyna- 
mite that  had  been  desiccated  for  a  sufficient  time  to  lose  all  of  its 
moisture  would  continue  to  lose  weight  in  an  empty  desiccator  (with- 
out any  desiccating  agent  present). 

Two  2-gram  samples  of  60  per  cent  dynamite  were  dried  for  three 
days  on  watch  glasses  over  sulphuric  acid,  and  then  immediately 


12 


2-1 


48 


54 


(50 


72 


78 


)         36          42 
DAYS 

FIGURE  3.— Result  of  exposure  of  dry  60  per  cent  dynamite  in  a  desiccator  at  33°  to  35°  C.  without  desic 

eating  agent. 

placed  in  clean  desiccators  without  any  drying  agent.  One  of  these 
was  kept  at  room  temperature  (17°  to  22°  C.),  the  other  in  a  constant- 
temperature  incubator  oven  at  a  temperature  of  33°  to  35°  C. 
Weighings  made  at  intervals  showed  a  continued  steady  loss  from 
the  sample  at  33°  to  35°,  whereas  the  sample  exposed  to  room  tem- 
perature gained  in  weight  at  first,  then  steadily  lost  until  at  the  end 
of  about  40  days  it  had  attained  its  original  weight.  In  the  table 
below  the  percentage  of  loss  or  gain  in  weight  recorded  represents 
the  variation  from  the  dry  weight  of  the  samples  after  having  been 
desiccated  three  days. 


DYNAMITE. 


27 


Change  in  weight  of  dried  samples  of  60  per  cent  dynamite  in  desiccators  containing  no 

desiccating  agent. 


Time  in 
desiccator. 

Change  in  weight. 

Sample  A  (17°-22°  C.). 

Sample  B 
(33°-35°  C.). 

Gain. 

Loss. 

Loss. 

Days. 

4 
7 
10 
13 
16 
20 
41 
77 
202 

Percent. 
0.36 
.35 
.30 
.25 
.20 
.20 

Per  cent. 

Per  cent. 
0.13 
.46 
.80 
1.10 
1.40 
1.75 
3.40 
5.35 
9.33 

0.05 
.67 
2.63 

It  is  often  desirable  to  make  a  weighing  at  a  shorter  interval  than 
72  hours,  and  to  obtain  an  approximation  of  the  true  moisture  by 
calculation.  An  extended  series  of  tests  was  made  to  determine 
what  factor  could  be  safely  used,  in  conjunction  with  a  weight 
taken  at  the  end  of  24  hours,  to  give  the  same  result  as  would  be 
obtained  by  desiccation  for  a  period  of  72  hours.  It  was  found  that 
the  influence  of  the  temperature  of  the  room  in  which  the  desiccator 
was  kept  was  so  marked,  and  the  difference  in  effect  between  differ- 
ent desiccating  agents,0  was  such  as  to  make  this  method  uncertain. 
At  the  best  only  an  approximation  can  be  obtained,  but  when  time 
is  more  important  than  accuracy  a  rough  approximation  to  the  true 
moisture  content  of  ordinary  dynamite  can  be  obtained  by  consid- 
ering the  loss  in  weight  over  sulphuric  acid  in  24  hours  to  be  90  per 
cent  of  the  total  moisture.  In  other  words,  the  loss  of  weight  in  24 
hours'  desiccation  multiplied  by  the  factor  1.11  will  be  an  approxi- 
mation to  the  true  moisture  content.  When  large  amounts  of  mois- 
ture are  present,  as  in  certain  types  of  coal-mining  explosives  con- 
taining water  added  as  a  constituent  of  the  explosive,  it  is  not 
advisable  to  attempt  the  use  of  such  a  factor.  In  such  cases  the 
loss  of  weight  on  desiccating  three  days  is  considered  as  the  total 


moisture. 


IN   VACUUM   DESICCATORS. 


The  evaporation  of  water  is  much  more  rapid  at  reduced  pressure 
than  under  atmospheric  pressure,  and  therefore  the  determination 
of  moisture  may  be  made  in  a  shorter  time  with  the  use  of  a  vacuum 
than  when  atmospheric  pressure  prevails  within  the  desiccator. 
If  nitroglycerin  were  perfectly  nonvolatile,  desiccation  in  a  vacuum 
would  probably  be  sufficiently  reliable  for  use  as  a  standard  method. 


a  See  table  on  p.  24. 


28  ANALYSIS   OF  BLACK  POWDER  AND  DYNAMITE. 

The  following  table  shows  the  results  obtained  when  samples  of  the 
same  dynamite  were  exposed  in  desiccators  of  similar  size  and  shape 
that  contained  the  same  desiccating  agent,  in  one  case  a  vacuum 
being  used  and  in  the  other  case  the  air  within  the  desiccator  being 
at  the  pressure  of  the  air  in  the  room. 

Results  of  desiccating  tests  with  and  without  vacuum  in  the  desiccator. 


Time  dried. 

Sample  in 
ordinary 
desiccator. 

Sample  in 
vacuum 
desiccator. 

Loss  of  moisture  in  24  hours 

Per  cent. 
5.34 

Per  cent. 
5.42 

Loss  of  moisture  in  48  hours                                                                

5.49 

5.63 

Loss  of  moisture  in  72  hours 

5.68 

5.80 

With  the  ordinary  type  of  desiccator,  containing  acid  in  the  bottom, 
moisture  is  removed  from  the  sample  much  more  rapidly  with  a 
vacuum  than  without,  other  conditions  being  equal.  For  example, 
in  a  4-inch  desiccator,  with  7  square  inches  of  acid  surface  on  which 
the  pressure  was  that  of  the  atmosphere,  the  loss  of  moisture  from 
a  powder  sample  containing  about  11  per  cent  of  water  was  only  54 
per  cent  of  the  total  in  6  hours,  83  per  cent  in  12  hours,  and  94  per 
cent  in  24  hours.  In  a  slightly  larger  desiccator  of  the  same  type, 
with  12  square  inches  of  acid  surface,  above  which  there  was  a 
vacuum,  the  loss  in  6  hours  was  91  per  cent,  in  12  hours  95  per 
cent,  and  in  24  hours  96.5  per  cent.  In  both  samples  a  practically 
constant  value  was  obtained  in  3  days. 

In  the  case  of  the  Hempel  desiccator,  containing  acid  above  the 
explosive  sample,  the  rate  of  loss  of  moisture  is  nearly  the  same  with 
or  without  vacuum. 

In  general  it  may  be  stated  that  any  type  of  vacuum  desiccator 
will  remove  in  12  hours  practically  all  the  moisture  from  dynamites 
and  even  from  permissible  explosives  containing  as  much  as  10  to 
12  per  cent  of  water,  the  result  thus  obtained  being  about  the  same 
as  that  given  by  3  days'  desiccation  without  vacuum. 

Vacuum  desiccation  for  a  longer  time  than  12  .hours  will  cause  a 
further  slight  loss,  which  is  probably  for  the  most  part  due  to  vola- 
tilization of  nitroglycerin. 

IN   A    DRY-AIR   CURRENT. 

When  a  current  of  air  previously  dried  by  being  passed  tarough  a 
calcium  chloride  tube,  or  through  sulphuric  acid,  is  passed  through 
a  mass  of  dynamite  in  a  suitable  sample  tube,  the  dynamite  gives  up 
its  moisture  to  the  dry  air.  Drying  may  be  very  quickly  effected  in 
this  manner,  because  of  the  fact  that  the  dry  air  comes  into  intimate 
contact  with  all  portions  of  the  explosive,  but  the  method  has  the 


DYNAMITE. 


29 


serious  defect  of  being  inaccurate,  owing  to  the  volatility  of  nitro- 
glycerin. 

In  desiccation  by  means  of  dry  air,  a  drying  tube  of  the  form 
shown  in  figure  4  is  usually  employed.  Sometimes  several  of  these 
tubes  are  connected  together  in  a  train.  The  dry  air  is  always  intro- 
duced at  the  bottom,  so  that  it  may  rise  through  the  explosive,  and 
a  weighed  sample  of  about  15  grams  is  generally  taken  for  the  deter- 
mination. 

Several  tests  were  made  to  determine  the  accuracy  of  this  method 
of  drying  samples  of  dynamite.  A  current  of  air  dried  by  passing 
through  sulphuric  acid  was  passed  through  a  sample  of  dynamite 
which  had  been  found,  by  desiccation  for  three  days  over  sulphuric 
acid,  to  contain  5.68  per  cent  of  moisture.  Weighings  at  intervals 
showed  loss  of  weight  as  follows. 

Loss  of  weight  of  dynamite  in  a  current  of  dry  air. 


Time 
dried. 

Loss  of 
weight. 

Hours. 

Per  cent. 

2 

1.47 

6 

4.29 

12 

5.20 

24 

5.50 

48 

5.70 

60 

5.80 

72 

5.86 

The  table  shows  that  at  the  end  of  48  hours  there  had  been  a  loss 
in  weight  approximately  corresponding  to  the  percentage  of  moisture 
found  in  the  explosive  by  the  standard  method.  The  constant  loss 
after  that  point  represents  volatilization  of  nitroglycerin,  although 
it  is  of  course  to  be  noted  that  the  loss  of  nitroglycerin  was  continu- 
ous, nitroglycerin  being  removed  from  the  time  the  air  first  began  to 
pass  through  the  sample.  How  inaccurate  this  method  is  may  be 
readily  understood  when  one  remembers  that  nitroglycerin  can  be 
completely  volatilized  by  bubbling  dry  air  through  it  for  a  sufficient 
length  of  time,  and  that  accordingly  any  sample  of  dynamite  would 
probably  reach  an  ultimate  value  in  which  the  loss  in  weight  would 
correspond  to  the  amount  of  moisture  plus  the  amount  of  nitroglyc- 
erin  present  in  the  sample. 


8UMMARY. 


The  most  satisfactory  method  for  the  determination  of  moisture 
consists  in  using  a  3-inch  watch  glass  containing  an  evenly  distrib- 
uted 2-gram  sample,  the  watch  glass  and  sample  being  placed  in  a 
desiccator  containing  sulphuric  acid,  and  being  weighed  at  the  expira- 
tion of  72  hours.  Care  should  be  taken  that  the  temperature  does  not 
vary  widely  from  a  mean  of  20°  C.  An  approximation  of  the  true 


30 


ANALYSIS   OP   BLACK   POWDEK   AND   DYNAMITE. 


moisture  content  of  the  sample  of  explosive  may  be  obtained  by  des- 
iccating in  the  manner  just  described  for  a  period  of  24  hours,  and 
multiplying  the  loss  in  weight  thus  found  by  the  factor  1.111,  or  the 
loss  in  a  vacuum  desiccator  for  24  hours  may  be  taken  without  fur- 
ther calculation  as  an  approximation  to  the  true  moisture  content 
as  determined  by  standard  methods. 

EXTRACTION    WITH    ETHER. 

Extraction  with  ether  removes  from  dynamite  not  only  nitro- 
glycerin,  but  also  any  resins  or  sulphur  that  may  be  present.     Aside 

from  resin  intentionally  admixed 
there  is  always  some  resin  present 
in  the  wood  pulp.  In  addition  to 
these  constituents,  in  dynamite 
small  amounts  of  oil  are  sometimes 
found,  having  been  introduced  from 
mixing  machines  or  packing  ma- 
chines. When  flour,  corn  meal,  or 
other  grain  or  cereal  products  are 
present  as  constituents  of  explo- 
sives a  small  amount  of  oil  from 
such  materials  is  also  found  in  the 
ether  extract.  Nitro toluenes,  par- 
affin, vaseline,  etc.,  are  not  normal 
FIGURE  4.-Drying  tube.  constituents  of  ordinary  dynamite, 

and  the  determination  of  these  substances  is  discussed  under  the 
type  of  explosive  in  which  they  occur  as  characteristic  components, 
but  it  is  to  be  noted  that  were  any  of  these  materials  present  in 
dynamite  they  would  be  found  in  the  ether  extract. 


REFLUX-CONDENSER   METHOD. 


A  sample  of  from  6  to  10  grams  of  the  explosive  is  weighed  in  either 
a  porcelain  Gooch  crucible  with  asbestos  mat  or  a  porous  alundum  ° 
crucible  of  about  25  c.  c.  capacity.  When  a  Gooch  crucible  is  used 
the  mat  should  be  light,  but  should  be  perfectly  coherent.  Such  a  mat 
is  prepared  in  the  bureau's  explosives  laboratory  as  follows:  Five 
grams  of  short-fiber  asbestos,  in  the  form  of  short  shreds,  free  from 
hard  lumps,  is  added  to  1  liter  of  water.  When  used  the  mixture  is 
well  shaken  and  about  10  c.  c.,  an  amount  sufficient  to  fill  the  crucible 
to  about  two-thirds  of  its  depth,  is  poured  into  the  crucible.  Suc- 
tion is  applied,  and  a  smooth  and  perfect  mat  is  almost  invariably 
produced.  The  crucible  and  mat  are  then  carefully  dried  for  some 
hours  at  100°,  weighed,  and  placed  in  a  desiccator.  For  extracting 
with  ether,  the  form  of  apparatus  found  most  satisfactory  is  the 


a  A  trade  name  for  artificially  prepared  porous  aluminum  oxide. 


DYNAMITE.  31 

Wiley  extractor,  as  shown  in  Plate  II,  A.  The  crucible  is  supported 
on  a  small  hanger  made  by  twisting  Xo.  18  copper  wire  into  suitable 
shape. 

In  performing  an  extraction  the  crucible,  with  its  weighed  sample 
of  explosive,  is  placed  in  the  hanger,  and  about  35c.c.  ofU.S.P.  ether 
(96  per  cent)  is  poured  in  several  portions  through  the  sample  into  the 
glass  extraction  tube.  Water  is  continuously  circulated  through  the 
cooling  coils  of  the  condenser.  The  ether  is  boiled  by  means  of  an 
electric  heater  or  a  vessel  of  hot  water  in  which  the  lower  part  of  the 
tube  is  immersed.  The  ether  vapor  condenses  on  the  surface  of  the 
metal  condenser,  the  condensed  ether  dropping  into  the  crucible  and 
percolating  through  the  sample  of  explosive.  The  temperature  is 
regulated  so  that  the  sample  will  be  kept  covered  with  ether  without 
any  overflow. 

When  a  vessel  of  hot  water  is  used  for  heating  the  tube,  the  ether 
partly  drains  out  of  the  crucible  during  a  change  of  water,  but  is  at 
once  replaced  by  a  fresh  supply.  This  intermittent  action  probably 
accomplishes  a  more  efficient  extraction  than  is  obtained  by  keeping 
the  sample  continuously  covered  with  ether.  The  extraction  with 
ether  is  continued  for  about  three-fourths  of  an  hour  for  most  explo- 
sives. This  period  is  usually  somewhat  longer  than  is  necessary  to 
remove  all  of  the  nitroglycerin,  but  it  is  desirable  to  carry  on  the 
extraction  long  enough  to  insure  the  complete  removal  of  material 
soluble  in  ether,  so  as  to  avoid  testing  for  completeness  of  extraction. 
If  for  any  reason  a  shorter  time  for  extraction  is  desirable,  the  extrac- 
tion is  continued  for  the  time  desired,  after  which  a  small  additional 
amount  of  ether  is  put  into  the  apparatus,  and  the  ether  passing 
through  the  crucible  is  evaporated  in  a  watch  glass  and  an  examina- 
tion made  for  residue.  If  residue  is  found,  complete  extraction  has 
obviously  not  been  accomplished. 

The  crucible  containing  the  portion  of  the  explosive  insoluble  in 
ether  is  placed  in  a  drying  oven  heated  to  about  100°  C.  This  shoulcl 
be  done  promptly,  since  the  evaporation  of  the  ether  with  which 
the  contents  of  the  crucible  are  saturated  lowers  the  temperature  of 
the  crucible  sufficiently  to  cause  the  precipitation  of  considerable 
moisture  upon  the  crucible  and  its  contents,  and  such  a  precipita- 
tion is  undesirable  as  it  necessitates  longer  drying.  Although  no 
loss  or  inaccuracy  in  analysis  is  liable  to  result  from  the  constituents 
of  the  explosives  becoming  wet  at  this  stage,  yet  for  uniform  results 
in  drying  it  is  usually  best  to  transfer  the  crucible  directly  from  the 
Wiley  extractor  to  the  drying  oven.  To  avoid  filling  the  drying  oven 
with  ether  vapors,  it  is  convenient  to  have  a  suction  flask  i  nd  carbon 
tube  near  the  Wiley  extractor,  and  as  soon  as  the  ether  extraction 
is  completed  the  crucible,  still  very  wet  with  ether,  may  be  placed  in 


32  ANALYSIS   OF   BLACK   POWDER  AND   DYNAMITE. 

the  carbon  tube  and  sucked  dry,  after  which  it  is  placed  in  the  drying 
oven. 

If  the  qualitative  examination  has  indicated  the  presence  of 
ammonium  nitrate,  the  drying  of  the  material  insoluble  in  ether 
should  be  carried  out  at  70°  C.  instead  of  100°  C.,  because  at  100° 
i*n  appreciable  loss  of  ammonium  nitrate  results  whereas  at  70°  the 
loss  is  slight. 

The  periods  of  drying  generally  adopted  are  five  hours  at  95°  to 
100°,  and  overnight  or  18  to  24  hours  at  70°  C.  Even  at  the  higher 
temperature  no  error  results  by  drying  overnight  unless  ammonium 
salts  or  other  volatile  ingredients  are  present.  A  shorter  time  than 
five  hours  is  probably  sufficient  in  most  cases,  but  the  five-hour 
period  has  been  adopted  to  cover  all  cases  and  obviates  any  necessity 
of  an  additional  check  weighing. 

The  loss  of  weight  represents  all  ether-soluble  material  plus  the 
moisture  originally  present  in  the  sample. 

The  ether  extract  is  transferred  from  the  glass  extraction  tube  to 
an  evaporating  dish  of  low  pattern  or  to  a  small  beaker  previously 
weighed.  The  extraction  tube  is  then  washed  out  with  a  small 
quantity  of  pure  ether,  which  is  added  to  the  ether  extract  in  the 
evaporating  dish.  The  contents  of  the  evaporating  dish  are  allowed 
to  evaporate  spontaneously;  a  number  of  hours  are  usually  allowed 
for  the  evaporation,  the  best  results  being  obtained  when  the  period 
is  overnight.  After  the  ether  has  evaporated,  the  residue  is  thor- 
oughly dried  by  leaving  the  dish  for  a  few  hours  in  a  vacuum  desic- 
cator. The  weight  is  then  noted;  it  is  usually  a  little  less  than  the 
total  loss  on  ether  extraction  minus  the  moisture  as  determined  by 
desiccation.  The  difference  is  due  to  volatilization  of  the  nitro- 
glycerin  during  the  evaporation  of  the  ether,  and  is  considered  later. 

A  more  nearly  correct  value  for  the  weight  of  material  removed  by 
ether  is  obtained  by  deducting  the  amount  of  moisture  determined  by 
desiccation  from  the  total  loss  of  weight  found  by  extraction,  the 
direct  weight  of  the  ether  extract  after  the  evaporation  of  ether 
being  used  only  as  a  check.  In  all  cases  ether  extraction  should  be 
made  in  duplicate,  one  sample  of  the  weighed  extract  being  used 
for  the  determination  of  the  nitroglycerin  with  the  nitrometer,  and 
the  other  sample  being  used  in  determining  the  other  constituents 
present. 

SUCTION    METHOD. 

In  the  laboratories  of  some  dynamite  works  extraction  with  ether 
is  made  without  any  form  of  continuous-extraction  apparatus;  the 
sample  in  the  Gooch  crucible  is  merely  washed  several  times  by 
pouring  ether  through  it,  applying  suction  after  each  addition  of 
ether.  This  method  involves  the  use  of  greater  quantities  of  ether, 


BUREAU    OF    MINES 


BULLETIN    51       PLATE   II 


.-1.     APPARATUS  FOR  ETHER  EXTRACTION.     WILEY  EXTRACTOR. 


B.     GRAVIMETRIC  BALANCE. 


DYNAMITE.  33 

and  the  objection  has  been  made  that  the  reduction  of  temperature 
resulting  from  the  evaporation  of  ether  causes  a  deposition  of  mois- 
ture from  the  air  current  drawn  through  the  sample,  this  moisture 
dissolving  out  small  amounts  of  the  water-soluble  nitrates  that  pass 
through  with  the  next  addition  of  ether. 

To  test  the  merits  of  this  method  in  comparison  with  the  usual 
extraction  method,  ether  extractions  were  made  on  a  large  number 
of  samples  of  45  per  cent  dynamite,  using  both  the  reflux-condenser 
method  and  the  suction  method.  In  the  latter  method  about  100 
c.  c.  of  ether  in  six  portions  was  passed  through  each  sample,  each 
portion  of  ether  being  allowed  to  stand  in  the  crucible  for  one  minute 
before  suction  was  applied.  The  suction  was  continued  for  periods 
of  one-half  minute  to  two  minutes  in  order  that  different  amounts  of 
air  might  be  drawn  through  the  samples.  The  samples  were  then 
dried  and  weighed  as  usual. 

In  general,  extraction  in  the  Wiley  apparatus  gave  slightly  lower 
results  than  the  suction  method,  although  in  most  cases  the  diff erence 
between  duplicate  samples  extracted  by  the  same  method  was  as 
great  as  the  variation  between  the  two  methods.  This  fact  is 
explained  by  the  lack  of  homogeneity  of  the  dynamite.  For  example, 
a  few  unusually  large  particles  of  wood  pulp  or  nitrate  in  one  sample 
may  cause  a  greater  variation  in  the  percentage  of  ether  extract  than 
the  variation  actually  due  to  the  method  of  extraction  employed. 

COMPARATIVE  EXTRACTIONS  WITH  ANHYDROUS  AND  U.  8.  P.  (96  PER 

CENT)  ETHER. 

To  ascertain  the  effect  of  the  purity  of  the  ether  used  for  extrac- 
tions, determinations  of  ether  extracts  were  made  on  several  types  of 
explosives,  and  on  various  carbonaceous  absorbents  used  in  dyna- 
mites. Duplicate  determinations  were  made  using  both  anhydrous 
ether  (distilled  over  sodium)  and  U.  S.  P.  (96  per  cent)  ether. 

Results  of  extractions  are  shown  in  the  following  table,  the  values 

given  being  the  percentage  of  loss  of  weight  noted  on  weighing  the 

insoluble  portion  after  drying  five  hours  at  95°  to  100°.     The  loss  of 

weight  in  each  case  therefore  includes  any  moisture  originally  present. 

67709°— Bull.  51—13 3 


34  ANALYSIS   OF   BLACK   POWDER   AND   DYNAMITE. 

Loss  of  weight  of  explosives  and  of  carbonaceous  absorbents  by  ether  extraction. 


Kind  of  sample. 

Kind  of  ether. 

U.  S.  P.  (96 
per  cent)  . 

Anhydrous. 

Dynamite  (A)                    

Per  cent. 
25.  86 
32.58 
40.77 
14.81 
13.18 
14.91 
1.81 
2.71 
2.59 
2.31 
8.84 
5.44 
5.98 
12.24 
13.30 
5.65 
6.23 
5.01 
7.74 
8.27 

Per  cent. 
25.69 
32.51 
40.74 
14.92 
13.12 
14.78 
1.71 
2.18 
2.20 
1.85 
8.02 
4.73 
5.48 
11.98 
12.75 
5.23 
5.88 
4.85 
7.40 
7.86 

Dynamite  (C)          -  

Wheat  flour                                          

Wheat  middlings      

Corn  meal  dry                          

Wood  pulp  dry  (1)                                         

Wood  pulp  dry  (2)          

Wood  pulp'(4)        

Wood  pulp  (5                             

Wood  pulp  (6                                                

Wood  pulp  (7            

Wood  pulp  (8                               

Wood  pulp  (9)        

Wood  pulp  (10)                  

Wood  pulp  (11)                                      

Wood  pulp  (12)      

Wood  pulp  (13)                                  

From  the  table  it  is  apparent  that  U.  S.  P.  ether  extracts  a  larger 
percentage  of  material  from  the  commonly  used  carbonaceous 
absorbents  than  does  anhydrous  ether,  which  is  practically  free  from 
alcohol.  It  is  probably  because  of  the  alcohol  present,  in  amounts 
up  to  about  4  per  cent,  that  U.  S.  P.  ether  shows  the  greater  extractive 
power. 

EFFECT  OF  MOISTURE  IN  DYNAMITE  ON  EXTRACTION  WITH  ETHER. 

Numerous  authorities  prescribe  that  the  ether  extraction  shall  be 
made  on  a  sample  previously  dried  to  constant  weight  in  a  desicca- 
tor.0 Presumably  this  specification  is  aimed  to  prevent  water- 
soluble  constituents  from  being  carried  through  in  the  ether  extract. 
Such  an  error  is  naturally  greater  as  the  amount  of  moisture  present 
in  the  dynamite  is  greater.  Accordingly  experiments  were  made  on 
mining  explosives  similar  to  ordinary  dynamite,  to  which  water  had 
been  added  as  an  additional  constituent  for  the  purpose  of  reducing 
the  temperature  of  explosion.  Two  explosives  containing  10.70  and 
5.70  per  cent  of  moisture,  respectively,  were  extracted  with  ether  IB 
the  usual  manner,  (1)  in  the  original  condition,  and  (2)  after  having 
been  dried  in  vacuum  desiccators  over  sulphuric  acid  for  24  hours, 
The  amounts  of  materials  soluble  in  ether  extracted  are  shown  in  the 
following  table. 


«  Guttman,  O.,  Schiess-und  Sprengmittel,  1910,  p.  162;  Kedesdy,  E.,  Sprengstofle,  1909,  p.  247;  Escales,  R. 
Die  Explosivstoffe,  vol.  3, 1908,  p.  204. 


DYNAMITE. 

Results  of  ether  extraction  of  two  explosives  in  different  conditions. 


35 


1 

2 

8 

4 

5 

Sample. 

Condition. 

Moisture. 

Extract. 

Difference. 

Percent. 

Percent. 

Percent. 

A 

{       i 

10.70 
.44 

28.52 
025.93 

j>           0.59 

B 

{       J 

5.70 
.45 

25.79 
025.43 

j             .36 

o  Calculated  to  explosive  in  original  condition. 

The  amount  of  moisture  present  in  the  dried  samples  was  found 
by  desk-rating  portions  of  each  sample  for  a  further  period  of  thj-ee 
days  in  ordinary  sulphuric-acid  desiccators. 

The  values  in  column  4  represent  the  total  loss  on  extraction  less 
the  moisture  content  of  the  sample,  all  results  being  expressed  as 
a  percentage  of  the  amount  of  original  undried  explosive. 

Assuming  that  the  extracts  from  the  samples  in  their  original 
condition  (condition  1)  are  larger  than  those  from  the  dried  samples 
(condition  2)  because  of  loss  of  water-soluble  nitrate  in  the  moisture 
taken  up  by  the  ether,  it  is  apparent  that  in  the  case  of  ordinary 
dynamite  containing  only  one  or  two  per  cent  moisture  any  loss  from 
this  source  is  negligible. 

DETERMINATION   OF   NITROGLYCERIN. 

The  nitrogen  of  organic  or  inorganic  nitrates  or  nitrites  is  readily 
evolved  as  nitric  oxide  (NO)  by  reaction  with  sulphuric  acid  and 
mercury  in  the  nitrometer.  A  determination  of  such  nitrogen  in 
the  extract  therefore  serves  as  a  means  of  calculating  the  amount 
of  nitroglycerin  present.  The  form  of  nitrometer  found  by  the 
authors  to  be  most  satisfactory  for  explosives  work  is  the  modified 
Lunge  nitrometer,  as  illustrated  in  Plate  III. 


THE    NITROMETER. 


This  instrument  °  consists  of  six  glass  parts  as  follows :  A  globe- 
shaped  reservoir  (a) ;  a  generating  bulb  (b)  of  about  300  c.  c.  capacity, 
the  generating  bulb  having  stopcocks  at  both  top  and  bottom  to 
permit  a  violent  agitation,  and  having  a  cup  above  which  communi- 
cates with  the  bulb  through  the  upper  stopcock;  a  second  globe- 
shaped  reservoir  (c),  to  which,  by  means  of  a  glass  multiple  connect- 
ing tube  and  rubber  tubing,  are  joined  a  compensating  burette  (d),  a 
reading  burette  (e) ,  and  an  additional  measuring  burette  (/) .  The  read- 
ing and  compensating  burettes  are  of  the  same  shape  and  size,  and 

«  The  description  has  been  taken  in  a  large  part  from  a  paper  by  J.  R.  Pitman  on  The  analysis  of  nitric 
and  mixed  acids  by  du  Font's  modification  of  the  Lunge  nitrometer,  Jour.  Soc.  Chem.  Ind.,  vol.  19,  1900, 
p.  983;  see  also  Lunge,  G.,  Du  Font's  nitrometer,  Jour.  Soc.  Chem.  Ind.,  vol.  20, 1901,  p.  100. 


36  ANALYSIS   OP  BLACK   POWDER  AND  DYNAMITE. 

are  blown  out  into  bulbs  at  the  top.  The  compensating  burette  is 
not  graduated.  Above  the  bulb  it  has  a  small  vertical  open  tube, 
which  is  sealed  when  the  instrument  is  standardized.  The  reading 
burette  is  calibrated  so  that  percentages  of  nitrogen  may  be  read 
therefrom,  and  is  marked  to  read  from  10  to  14  per  cent,  being 
graduated  to  one-hundredths  of  1  per  cent.  Between  171.8  and 
240.4  c.  c.  of  gas  must  be  generated  to  obtain  a  reading;  that  is, 
the  10  per  cent  mark  represents  the  volume  of  171.8  c.  c.  of  NO 
at  20°  and  760  mm.  pressure,  containing  0.1  gram  of  nitrogen;  the 
14  per  cent  mark  is  equal  to  240  c.  c.  NO  under  the  same  condi- 
tions, representing  0.14  gram  nitrogen. 

The  compensating  burette  is  supported  by  a  ring;  the  generating 
bulb  is  supported  just  above  each  stopcock  by  forked  holders, 
curved  so  as  to  retain  the  bulb  in  place.  In  order  to  remove  the  gen- 
erating bulb  it  needs  only  to  be  raised  slightly  and  brought  forward, 
the  manipulation  of  a  screw,  as  with  an  ordinary  clamp,  being  thus 
avoided.  The  two  reservoirs  and  the  reading  burette  are  supported 
by  ring  clamps,  these  clamps  having  milled  rollers  at  the  shank; 
they  are  moved  up  and  down  vertical  racks  by  means  of  hand 
screws,  the  rollers  being  so  arranged  in  conjunction  with  the  ver- 
tical racks  that  the  weight  of  the  part  presses  them  down  and  acts 
as  a  brake,  thus  preventing  their  moving  when  not  being  manipulated. 

Having  arranged  the  apparatus  and  filled  the  compensating, 
reading,  and  generating  tubes  as  well  as  their  connections  with 
mercury,  the  next  step  is  to  standardize  the  instrument.  Twenty 
to  thirty  cubic  centimeters  of  sulphuric  acid  is  run  into  the  gener- 
ating bulb  through  the  cup  at  the  top,  and  at  the  same  time  about 
210  c.  c.  of  air  is  let  in;  the  cocks  are  then  closed  and  the  bulb  is  well 
shaken;  this  shaking  thoroughly  desiccates  the  air,  which  is  then 
run  into  the  compensating  burette  until  the  murcury  is  about  on  a 
level  with  the  12.50  per  cent  mark  on  the  reading  burette,  the  two 
burettes  being  held  at  the  same  height.  The  compensating  burette 
is  then  sealed  off  at  the  top.  A  further  quantity  of  air  is  desiccated 
in  the  same  manner  and  run  over  into  the  reading  burette  until  the 
height  of  mercury  in  the  reading  burette  stands  at  about  the  12.50 
per  cent  mark.  The  cocks  are  then  closed,  and  a  small  piece  of 
glass  tubing,  filled  with  sulphuric  acid  (not  water),  and  bent  in  the 
form  of  a  U,  is  attached  to  the  outlet  of  the  reading  burette.  When 
the  mercury  columns  are  about  balanced  and  the  inclosed  air  has 
been  cooled  to  room  temperature,  the  cock  is  again  carefully  opened, 
and  when  the  sulphuric  acid  balances  in  the  U  tube,  and  the  mercury 
columns  in  both  burettes  are  therefore  at  the  same  level,  the  air  in 
each  tube  is  subject  to  the  same  conditions,  namely,  atmospheric 
temperature  and  pressure.  A  reading  is  now  made  from  the  burette, 


BUREAU    OF    MINES 


BULLETIN    51       PLATE    III 


NITROMETER. 


DYNAMITE.  37 

and  the  barometric  pressure  and  temperature  are  carefully  noted. 
the  well-known  formula 


~  P(273+f)(l-  -000180 

the  volume  this  inclosed  air  would  occupy  at  a  pressure  (P)  of  29.92 
inches  of  mercury  (760  mm.)  and  at  a  temperature  (t)  of  20°  C.  is 
determined.  The  cock  is  again  closed  and  the  reservoir  and  reading 
hurette  carefully  adjusted  so  as  to  bring  the  air  in  the  reading  burette 
to  the  calculated  volume  and  the  mercury  in  the  compensating  burette 
to  the  same  level  as  the  mercury  in  the  reading  burette.  A  strip  of 
paper  is  now  pasted  on  the  compensating  burette  at  the  level  of  the 
mercury,  and  the  standardization  is  then  complete. 

There  is,  however,  another  and  shorter  method  of  standardization 
than  the  one  described  above.  It  is  well  known  that  the  quality  of  the 
sulphuric  acid  used  in  the  nitrometer  will  materially  affect  the  results. 
To  ascertain  whether  sulphuric  acid  is  suitable  for  use  in  making  nitro- 
gen determinations  in  the  nitrometer  a  determination  is  made  on 
chemically  pure  dry  potassium  nitrate  and  the  reading  obtained  in 
the  nitrometer  is  compared  with  the  theoretical  percentage  of  nitrogen 
in  potassium  nitrate.  In  applying  this  procedure  to  the  standardiza- 
tion of  the  nitrometer  the  compensating  burette  is  filled  with  desic- 
cated air,  as  described  above,  and  1  gram  of  potassium  nitrate,  dis- 
solved in  2  to  4  c.  c.  of  water,  is  introduced  into  the  generating  bulb, 
the  cup  is  washed  with  20  c.  c.  of  95  to  96  per  cent  sulphuric  acid  in 
three  or  four  portions,  and  each  portion  is  run  separately  into  the 
bulb.  The  gas,  when  generated,  is  run  over  into  the  reading  burette, 
and  the  mercury  columns  in  both  burettes  are  leveled,  so  that  the 
mercury  in  the  reading  burette  is  also  at  13.87,  the  theoretical  per- 
centage of  nitrogen  in  potassium  nitrate.  A  strip  of  paper  is  pasted 
on  the  compensating  burette  at  the  level  of  the  mercury,  and  the 
standardization  is  then  accomplished. 

This  method  of  standardizing  offers  many  advantages  over  that 
first  described,  among  which  may  be  mentioned  that  no  readings  of 
temperature  or  pressure  are  necessary.  Probably  the  greatest 
advantage  is  that  if  the  acid  used  in  standardizing  should  contain 
impurities,  which  might  otherwise  affect  the  result,  the  error  is  en- 
tirely compensated  and  corrected  in  subsequent  work;  that  is  to  say, 
the  instrument  having  been  so  standardized  that  the  reading  gives  the 
theoretical  percentage  of  nitrogen  in  potassium  nitrate,  the  results 
will  be  accurate  when  testing  other  substances  so  long  as  the  same 
quantity  of  sulphuric  acid  from  the  same  lot  is  used. 

It  must,  of  course,  be  understood  that  once  having  standardized 
the  instrument  with  a  certain  lot  of  acid  no  different  lot  of  acid  can 
be  used  without  restandardizing.  In  order  to  avoid  slight  differences 


38  ANALYSIS  OF  BLACK  POWDER  AND  DYNAMITE. 

in  results  due  to  variations  in  the  acid,  it  is  advisable  to  reserve  a 
sufficiently  large  uniform  stock  of  acid,  for  example,  a  carboy  full, 
for  nitrometer  use. 

The  additional  measuring  burette,  with  which  this  type  of  nitrom- 
eter is  provided,  known  as  the  "  universal  tube"  (/,  PL  III),  is  simply  a 
straight  burette,  marked  to  read  from  0  to  100  in  percentages  and 
graduated  to  one-tenth  of  1  per  cent.  The  tube  is  of  such  a  size  that 
0.30  gram  of  NO  (or  y^j  gram-molecule  of  NO)  under  standard 
conditions  of  temperature  and  pressure  (20°  and  760  mm.)  fills  it  to 
the  100  mark. 

If  it  is  desired  to  read  the  percentage  of  nitrogen  direct,  0.14  gram 
of  substance  is  weighed  out;  if  the  percentage  of  NO2  is  desired, 
0.46  gram  of  substance  is  weighed  out.  Consequently,  if  1.01  grams 
of  potassium  nitrate,  0.63  gram  of  nitric  acid,  or  0.85  gram  of  sodium 
nitrate,  are  used,  the  results  can  be  read  directly  as  percentages  of 
the  original  substance. 

This  method  is  convenient  when  it  is  not  certain  that  the  reading 
will  fall  within  the  limits  of  the  graduations  in  the  ordinary  measur- 
ing burette. 

The  " universal  tube"  is  found  particularly  advantageous  when, 
for  example,  the  amount  of  nitroglycerin  in  a  sample  is  so  small  that 
the  volume  of  gas  generated  is  insufficient  to  fill  the  large  reading 
burette  to  its  graduated  portion.  The  volume  of  gas  generated  from 
any  amount  of  nitroglycerin  up  to  about  0.75  gram  may  be  read  in 
the  ''universal  tube."  Readings  in  this  measuring  tube  can  be  as 
accurately  made  as  in  the  regular  reading  burette. 

PROCEDURE. 

To  determine  the  amount  of  nitroglycerin  in  the  ether  extract  of  a 
dynamite,  the  sample  from  which  the  ether  has  been  evaporated  is 
dissolved  in  5  to  10  c.  c.  of  sulphuric  acid  (specific  gravity,  1.84)  and 
transferred  to  the  generating  bulb  of  the  nitrometer,  the  beaker  and 
the  cup  of  the  nitrometer  being  rinsed  with  several  further  additions 
of  acid  until  20  to  25  c.  c.  has  been  used.  If  the  quantity  of  nitro- 
glycerin present  is  too  great,  the  sample  dissolved  in  sulphuric  acid 
is  transferred  to  a  burette  and  an  aliquot  part  run  into  the  nitrometer 
cup  and  washed  into  the  generator  with  about  20  to  25  c.  c.  of  sul- 
phuric acid.  The  maximum  amount  of  pure  nitroglycerin  used  should 
be  not  greater  than  0.75  gram  in  order  that  the  gas  generated  will  not 
exceed  the  volume  of  the  reading  burette. 

The  generator  is  then  shaken  gently  until  the  generation  of  gas 
has  forced  out  all  but  about  60  to  75  c.  c.  of  the  mercury,  the  reser- 
voir being  lowered  if  necessary  in  order  to  reduce  the  amount  of 
mercury  to  this  extent.  The  cock  at  the  bottom  of  the  generator 
is  then  closed  and  the  generator  shaken  violently  for  about  two  to 


DYNAMITE. 


39 


three  minutes.  After  allowing  all  bubbles  to  separate  from  the 
reaction  mixture,  the  gas  is  transferred  to  the  reading  burette,  the 
surf a<v  <>f  the  mercury  in  the  burette  is  brought  to  the  same  level 
as  that  in  the  compensating  burette  when  the  dry  air  in  the  com- 
pensating burette  occupies  the  standard  volume  indicated  by  the 
strip  of  paper  attached  in  calibrating. 

The  gas  is  allowed  to  stand  for  a  few  minutes  to  obtain  an  equi- 
librium of  temperature,  the  levels  being  readjusted  if  necessary, 
and  the  reading  is  noted.  This  reading  divided  by  18.50  equals  the 
weight  of  nitroglycerin  in  the  sample  used  for  the  determination. 

A  more  or  less  serious  error  to  be  considered  in  the  determination 
of  nitroglyceiin  is  that  introduced  by  losses  due  to  volatilization 
of  the  nitroglycerin  during  the  evaporation  of  the  ether.  To  deter- 
mine the  effect  of  the  rapidity  of  evaporation  on  the  amount  of 
nitroglycerin  lost,  weighed  samples  (0.6  to  0.7  gram)  of  nitroglycerin 
were  placed  in  100  c.  c.  beakers,  tieated  with  50  c.  c.  of  ether,  the 
ether  evaporated  at  different  rates,  and  the  samples  dried  in  vacuum 
desiccators  to  remove  the  moisture  taken  up  during  the  evaporation 
of  the  ether.  Nitrogen  was  then  determined  by  means  of  the  nitrom- 
eter, the  weight  of  nitroglycerin  being  calculated  from  the  nitrom- 
eter reading.  The  results  obtained  are  tabulated  below: 

Loss  of  nitroglycerin  on  evaporating  ether  extract. 
[Determinations  by  J.  H.  Hunter.] 


1 

2 

3 

4 

5 

6 

7 

Sample. 

Original 
weight  of 
sample. 

Weight  of 
residue 
after  evap- 
oration of 
ether. 

Nitrometer 
reading. 

Weight  of 

found  by 
nitrometer.* 

Loss  of 
nitro- 
glycerin 
(2-5). 

Method  of  evaporation. 

1 

Gram. 
0  6469 

Or  am. 
0  6458 

Percent. 
11  73 

Gram. 
0  6389 

Gram. 
0  0080 

2  
3  

.6328 
.0212 

.6318 
.6140 

11.53 
11.17 

.6280 

.  l  UM 

.0048 
.0128 

night. 
Do. 
Gentle  boiling 

4 

.6375 

6  0268 

Do 

5 

6167 

11  31 

61t>0 

0039 

Do 

t  

.6664 

.6660 

11.96 

05  14 

0152 

Current  of  compressed  air 

7  

.0773 

.6710 

12.10 

.6590 

.0183 

blown  over  beaker. 
Do 

Weight  of  nitroglycerin = nitrometer  reading -8- 18.50. 


ft  Loss  of  weight. 


No  attempt  was  made  to  obtain  constant  weight  after  evaporation 
of  the  ether,  the  samples  being  left  hi  vacuum  desiccators  only  long 
enough  to  remove  most  of  the  water;  hence  the  weights  in  column 
3  are  greater  than  the  weights  of  nitroglycerin  calculated  from  the 
nitrogen  found  (column  5). 

The  figures  in  column  6  represent  the  differences  between  the 
weights  in  columns  2  and  5. 


40  ANALYSIS   OF   BLACK   POWDER   AND   DYNAMITE. 

It  was  noted  that  rapid  removal  of  the  ether,  either  by  means  of 
gentle  heating  or  by  means  of  an  air  current,  caused  a  greater  loss 
of  nifcroglycerin  than  did  slow  spontaneous  evaporation  at  room 
temperature,  the  only  exception  being  in  the  case  of  sample  5,  with 
which  the  loss  of  nitroglycerin  was  only  0.0039  gram,  the  ether  being 
volatilized  by  gentle  boiling.  The  large  loss  noted  with  sample  4 
was  probably  due  to  spurting. 

Such  losses  as  are  shown  in  the  table  do  not  greatly  affect  the 
determination  of  nitroglycerin  in  a  sample  of  dynamite.  Thus,  in 
analyzing  a  6-gram  sample  of  dynamite,  a  loss  of  0.01  gram  of  nitro- 
glycerin would  be  equivalent  to  only  0.17  per  cent  of  the  original 
sample.  The  importance  of  the  error  is  of  course  greater  as  the 
percentage  of  nitroglycerin  in  the  sample  is  less. 

Evaporation  in  the  Mi-jar  evaporator. — An  improved  method  of 
removing  the  ether  from  the  ether  extract  without  appreciable  loss 
of  nitroglycerin  was  devised  by  A.  L.  Hyde  in  the  bureau's  labora- 
tory. The  beaker  containing  the  ether  solution  is  placed  on  a 
ground-glass  plate  and  covered  by  a  glass  bell  jar  about  6  inches  in 
diameter  and  8  inches  high,  having  two  tubulures,  one  at  the  top 
and  one  on  the  side,  each  opening  being  fitted  with  a  perforated 
stopper  and  delivery  tube.  A  rapid  current  of  compressed  air, 
dried  by  passage  through  concentrated  sulphuric  acid,  in  two  wash 
cylinders,  is  allowed  to  enter  through  the  glass  tube  in  the  top  of  the 
bell  jar,  the  lower  end  of  the  tube  being  about  one-half  inch  above 
the  surface  of  the  ether  solution  in  the  beaker.  The  air  current  is  so 
regulated  that  a  marked  "  dimple"  is  made  in  the  surface  of  the 
solution,  care  being  taken  to  prevent  any  loss  by  spattering.  The 
possibility  of  acid  being  mechanically  carried  over  from  the  cylin- 
ders is  avoided  by  connecting  an  empty  trap  between  the  cylinders 
and  the  bell  jar.  The  ether  vapors  pass  out  through  the  glass  tube 
in  the  side  tubulure  and  may  be  conducted  out  of  the  laboratory 
through  a  rubber  tube  passing  to  a  hood  or  out  of  a  window. 

The  low  temperature  produced  by  the  rapid  evaporation  of  the 
ether  minimizes  the  volatilization  of  the  nitroglycerin,  and  the  fact 
that  the  air  is  thoroughly  dried  prevents  any  deposition  of  moisture 
in  the  beaker,  so  that  it  is  not  necessary  to  desiccate  the  residue 
after  the  ether  has  entirely  volatilized. 

The  following  preliminary  tests  show  the  efficiency  of  the  method: 
A  weighed  quantity  of  nitroglycerin  was  dissolved  in  50  c.  c.  of  ether, 
the  ether  evaporated  as  described,  and  the  residue  in  the  beaker 
weighed  at  intervals. 


DYNAMITE.  41 

Loss  of  nitroglycerin  by  evaporation  of  ether  solution  in  bell-jar  evaporator. 


Time  of 
evapora- 
tion. 

Weight  of  sample. 

A 

B 

C 

D 

Hours. 
0 
2 
3 
4 
6 
6 
7 
9 
11 
14 

Grams. 
02.838 
3.176 
2.941 
2.881 
2.863 
2.856 
2.851 
2.843 
2.841 
2.837 

Gram*. 
aS.236 
3.359 
3.286 
3.262 
3.251 
3.245 
3.241 
3.236 
3.235 
3.234 

Grams. 
02.979 
3.189 

Grams. 
02.620 

2.801 

3.037 

2.644 

2.987 
2.984 
2.978 
?,977 

2.623 
2.621 
2.619 
2.618 

•  Original  weight  of  nitroglycerin. 

U.  S.  P.  ether  (96  per  cent)  was  used  in  tests  A  and  B,  and  alcohol- 
free  ether  (distilled  over  sodium)  in  tests  C  and  D.  When  the  96  per 
cent  ether  was  used  a  distinct  odor  of  acetic  aldehyde  was  noticed 
and  the  rate  of  loss  of  weight  was  slightly  lower,  due  no  doubt  to  the 
presence  of  alcohol  in  the  ether. 

It  is  apparent  from  the  above  results  that  this  method  offers  a  con- 
venient and  rapid  method  of  removing  the  ether  without  appre- 
ciable loss  of  nitroglycerin.  Evaporation  for  about  six  hours 
removes  the  ether  sufficiently  to  permit  determination  of  the  nitro- 
glycerin in  the  nitrometer. 

DETERMINATIONS   OF   SULPHUR,  RESINS,  ETC. 

The  sulphur  used  in  dynamite  is  the  form  known  as  crushed  brim- 
stone. It  is  soluble  in  about  100  parts  of  ether  at  23.5°  C.,tt  and 
unless  present  in  large  amount  in  the  sample  of  explosive  being 
analyzed  it  will  all  be  removed  by  the  extraction  with  ether.  How- 
ever, when  a  considerable  amount  of  sulphur  crystallizes  out  in  the 
ether  extract,  it  is  always  advisable,  after  the  water  extraction,  to 
make  a  further  extraction  of  the  explosive  with  carbon  disulphide, 
in  order  to  insure  the  complete  removal  of  the  sulphur. 

As  already  mentioned,  the  analysis  of  an  explosive  is  carried  out 
in  duplicate,  one  sample  of  the  ether  extract  being  used  lor  the  de- 
termination of  nitroglycerin,  the  duplicate  sample  being  used  for  the 
determination  of  sulphur,  resins,  etc.  The  duplicate  sample  is  treated 
as  follows:  The  weighed  extract  is  redissolved  in  a  mixture  of  ether 
and  alcohol  previously  neutralized  with  standard  alkali.  The  solu- 
tion thus  obtained  is  titrated  with  standard  alcoholic  potash  to  deter- 
mine resins,  phenolphthalein  being  used  as  an  indicator.  Determi- 
nations of  a  number  of  samples  of  commercial  rosin  (colophony) 
gave  rather  uniform  results,  1  c.  c.  of  normal  alkali  being  found 

•  Gody,  L.,  Traite  theorique  et  pratique  des  matieres  explosives,  1907,  p.  85. 


42 


ANALYSIS   OF   BLACK   POWDER   AND   DYNAMITE. 


equal  to  0.34  gram  of  rosin,  which  agrees  with  the  value  given  by 
Lewkowitsch.0 

After  titration  a  large  excess  of  alcoholic  potash  is  added  and  the 
mixture  is  heated  on  the  steam  bath,  preferably  overnight,  in  order 
to  saponify  the  nitroglycerin.  It  must  be  remembered  that  nitro- 
glycerin  so  treated  saponifies  slowly.  Hence  the  reaction  must  not 
be  hastened  by  heating  to  a  higher  degree  than  that  obtained  on  a 
water  bath,  as  an  explosion  may  result.  When  saponification  is  com- 
plete the  residue  left  upon  evaporation  is  shaken  with  water  and  ether 
and  separated  in  a  separatory  funnel.  Any  oily  material  (vaseline, 
paraffins,  etc.)  that  can  not  be  saponified  is  dissolved  in  the  ether  and 
may  be  weighed  after  evaporation.  The  water  solution  is  acidified 
with  hydrochloric  acid  and  treated  with  bromine  to  oxidize  the 
sulphur.  Any  rosin  that  was  originally  present  will  have  formed  a 
soap  with  the  alkali;  the  acid  decomposes  this  soap,  and  the  rosin 
separates  out  from  the  acid  liquid,  floats  on  it,  and  may  be  readily 
removed,  dried,  and  weighed,  the  weight  serving  as  a  check  on  the 
results  of  titration.  The  sulphur  is  oxidized  to  sulphuric  acid  by  the 
bromine  and  may  be  determined  by  precipitation  as  barium  sulphate. 

Sulphur  may  be  separated  from  nitroglycerin  by  a  method  depend- 
ing on  the  fact  that  nitroglycerin  is  soluble  in  70  per  cent  acetic  acid, 
whereas  sulphur  dissolves  only  slightly  in  either  glacial  or  70  per  cent 
acetic  acid.  The  extent  to  which  sulphur  dissolves  in  acetic  acid 
was  determined  by  experiments  with  both  brimstone  and  flowers  of 
sulphur,  in  both  cases  the  material  being  pulverized  so  as  to  pass 
through  an  80-mesh  sieve. 

One  gram  of  sulphur  was  digested  in  100  c.  c.  of  acetic  acid  for  a 
definite  period  of  time;  the  mixture  was  then  washed  on  to  a  weighed 
Gooch  crucible,  dried  for  five  hours  at  70°,  and  weighed.  The  loss  in 
weight  represented  the  amount  of  sulphur  dissolved  by  100  c.  c.  of 
acid.  The  results  were  as  follows: 

Solubility  of  sulphur  in  acetic  acid. 
[Determinations  by  J.  H.  Hunter.] 


Form  of  sulphur. 

100  c.  c.  of  70  per  cent  acetic 
acid. 

100  c.  c.  of  glacial  acetic  acid. 

Temper- 
ature. 

Time. 

Weight  of 
sulphur 
dissolved. 

Temper- 
ature. 

Time. 

Weight  of 
sulphur 
dissolved. 

c  C. 
{           25 

J            25 
80 
80 
25 
25 
180 
80 

Hours. 
1 
25 
1 
1 
20 
20 
1 
1 

Gram. 
0.000 
.000 
.0226 
.0127 
.0115 
.  0090 
.0027 
.0036 

0  C. 

25 
25 
80 
80 

Hours. 
1 
1 
1 
1 

Gram. 
0.  0338 
.  0354 
.1658 
.1464 

a  Lewkowitsch,  J.,  Chemical  technology  and  analysis  of  oils,  fats,  and  waxes,  vol.  1,  1909,  p.  502. 


DYNAMITE.  43 

These  determinations  show  that  sulphur  (brimstone)  can  be  sepa- 
rated from  nitroglycerin  by  means  of  acetic  acid  (70  per  cent)  at  ordi- 
nary room  temperature  without  appreciable  loss  of  the  sulphur. 

EXTRACTION    WITH    WATER. 

The  determination  of  water-soluble  constituents  is  made  on  the 
dried  and  weighed  residues  left  in  the  crucibles  after  extraction  with 
ether.  The  apparatus  used  consists  of  an  ordinary  heavy-walled 
side-neck  suction  flask  provided  with  a  rubber  stopper,  through  which 
passes  a  carbon  filter  tube.  The  crucible  is  inserted  in  the  top  of  the 
filter  tube,  a  tight  joint  being  obtained  by  means  of  a  short  length 
of  thin-walled  rubber  tubing.  As  the  analysis  is  made  hi  duplicate, 
two  suction  flasks  so  arranged  are  connected  to  a  Y  tube,  and  both 
samples  are  extracted  at  once.  A  Bunsen  valve  or  an  empty  bottle 
to  serve  as  a  trap  should  be  inserted  between  the  Y  tube  and  the 
suction  pump  to  guard  against  any  tendency  of  the  water  to  "suck 
back.'7 

Cold  water  is  used  for  the  extraction  because  hot  water  would 
partly  gelatinize  any  starch  that  might  be  present,  and  hot  water 
would  also  remove  more  soluble  organic  material* from  the  wood  pulp. 
The  water  is  passed  through  each  sample  in  small  quantities  (about 
20  c.  c.)  at  a  tune.  The  sample  is  covered  with  water,  allowed  to  stand 
a  short  time,  and  suction  applied  until  all  the  water  has  passed  into 
the  flask.  This  process  is  repeated  until  at  least  200  c.  c.  of  water  has 
been  used.  If  each  portion  of  water  is  allowed  to  stand  on  the  sample 
for  a  short  tune  and  then  thoroughly  sucked  out,  this  quantity  of 
water  is  more  than  sufficient  for  complete  extraction,  but  in  case  of 
doubt  a  few  drops  of  the  last  portions  of  the  filtrate  is  tested  by  evapo- 
ration on  a  glass  plate. 

If  starch  is  present  the  filtration  often  proceeds  very  slowly  because 
of  the  tendency  of  the  starch  to  separate  at  the  bottom  of  the  crucible 
and  form  an  almost  impermeable  layer  on  top  of  the  asbestos  mat. 
In  such  cases  the  use  of  stronger  suction  simply  increases  the  dens  it  v 
of  this  mass  and  retards  rather  than  aids  filtration.  When  any  con- 
siderable quantity  of  starch  has  been  detected  in  the  qualitative 
examination,  it  is  advisable  to  make  use  of  porous  alundum  crucibles 
for  the  analysis,  since  these  allow  the  filtrate  to  pass  through  the 
walls  above  the  dense  material  at  the  bottom.  With  these  crucibles 
it  is  necessary  to  use  carbon  tubes  of  such  diameter  that  the  crucible 
projects  the  greater  part  of  its  depth  into  the  tube,  being  held  by  the 
rubber  about  one-fourth  inch  from  its  top.  If  this  is  not  done  there 
is  a  tendency  for  the  filtrate  to  leak  out  of  the  crucible  above  the 
rubber. 


44  ANALYSIS   OF   BLACK   POWDEK  AND  DYNAMITE. 

These  porous  crucibles  have  been  found  decidedly  convenient, 
especially  in  the  case  of  materials  that  tend  to  clog  the  ordinary 
Gooch  crucible. 

The  water  extraction  having  been  completed,  the  crucibles,  with 
their  contents,  are  again  placed  in  the  drying  oven  and  dried  for  five 
hours  at  about  95  to  100°  C.  No  additional  loss  results  from  longer 
drying  at  this  temperature,  and  frequently  to  save  time  samples  are 
dried  overnight.  After  cooling  in  a  desiccator  the  crucibles  are 
weighed  and  the  loss  of  weight  noted.  This  loss  of  weight  repre- 
sents the  total  water-soluble  material,  and,  in  addition  to  the  water- 
soluble  salts  detected  in  the  qualitative  examination,  includes  organic 
extract  from  the  wood  pulp,  flour,  or  other  absorbent.  When  cereal 
products  are  present  the  amount  of  organic  material  thus  extracted 
may  amount  to  2  per  cent  or  more,  including  sugars,  etc.,  that  form 
constituent  parts  of  the  grain.  Frequently  the  antacid  used,  generally 
calcium  carbonate  or  magnesium  carbonate,  is  attacked  by  acid 
decomposition  products  from  the  nitroglycerin,  a  portion  of  the  car- 
bonate being  thereby  converted  to  nitrate  or  nitrite.  In  such  cases 
some  calcium  or  magnesium  is  found  in  the  water  extract. 

Usually  the  only  water-soluble  constituent  to  be  considered  in  an 
ordinary  dynamite  is  an  alkaline  (sodium  or  potassium)  nitrate. 
When  an  approximate  analysis  only  is  desired  it  is  generally  con- 
sidered sufficient  to  regard  the  total  loss  of  weight  on  extraction  as 
nitrate,  but,  as  shown  above,  this  frequently  gives  erroneous  results. 

DETERMINATION    OF  ALKALINE    NITRATES. 

The  method  best  suited  for  determination  of  nitrates  is  the  follow- 
ing: An  aliquot  portion  of  the  water  extract  is  evaporated  to  dryness 
on  a  water  bath  and  the  residue  gently  ignited  to  burn  off  the  organic 
matter.  After  cooling,  the  sides  of  the  evaporating  dish  are  washed 
down  with  a  few  cubic  centimeters  of  water,  about  1  c.  c.  of  nitric 
acid  is  added,  the  evaporation  repeated,  and  the  residue  heated  gently 
over  a  burner  until  just  fused,  or  the  residue  is  dried  in  an  oven  at 
about  120°  C.  The  treatment  with  nitric  acid  is  necessary  for  the 
complete  conversion  to  nitrate  of  any  nitrite  resulting  from  burning 
off  the  organic  matter.  The  treatment  should  be  repeated  until  the 
weight  of  the  residue  is  constant. 

The  weighed  residue  is  calculated  as  percentage  of  nitrate  in  the 
original  explosive.  Since  this  weight  necessarily  includes  any  non- 
volatile water-soluble  impurities  originally  present  in  the  nitrate,  as 
iron,  aluminum,  chlorides,  sulphates,  etc.,  for  an  exact  analysis  it  is 
necessary  to  ascertain  the  amount  of  such  impurities  by  volumetric 
or  gravimetric  determinations  on  fresh  aliquot  portions  of  the  water 
extract,  or  a  direct  determination  of  the  true  nitrate  content  may  be 
made  in  the  nitrometer  as  described  on  the  folio  whig  page. 


DYNAMITE. 


45 


DETERMINATION    OP   ALKALINE    NITRATES    BY   MEANS    OP  THE    NITROMETER. 

An  aliquot  portion  of  the  water  extract  estimated  to  contain 
the  proper  amount  of  nitrate  for  determination  in  the  nitrometer 
(about  0.6  to  0.8  gram  of  NaNO3  or  0.8  to  1.0  gram  of  KNO3  for 
the  type  of  nitrometer  previously  described,  p.  35)  is  evaporated 
almost  to  dryness  on  a  steam  bath  and  transferred,  by  means  of  as 
little  water  as  possible,  to  the  cup  of  the  nitrometer.  The  amount  of 
water  used  should  not  exceed  20  c.  c.  This  solution  is  drawn  into 
the  generator,  and  30  to  40  c.  c.  of  sulphuric  acid  (95  to  96  per  cent) 
is  added  slowly,  in  small  quantities  at  first  to  avoid  generating  suf- 
ficient heat  to  crack  the  glass.  Because  of  the  dilution  of  the  acid 
the  generation  of  the  gas  proceeds  much  more  slowly  than  in  the 
determination  of  nitroglycerin,  and  it  is  necessary  to  shake  the  gen- 
erator for  a  total  time  of  about  8  to  10  minutes  in  order  to  be  certain 
that  the  reaction  is  complete.  The  volume  of  gas  is  measured  and 
the  percentage  of  nitrate  is  calculated  in  the  same  manner  as  in  the 
case  of  nitroglycerin.  This  method  is  excellent  for  use  as  a  check  or 
for  an  exact  determination  of  the  actual  nitrate  content. 

Tests  made  on  a  1  per  cent  solution  of  pure  potassium  nitrate  by 
both  the  gravimetric  and  volumetric  methods  described  above  gave 
results  as  follows: 

Results  of  determinations  of  nitrates  in  a  water  solution  by  the  gravimetric  and  by  the 

volumetric  method. 

[Determinations  by  J.  H.  Hunter.] 


Test 
No. 

Volume  of 
solution 
used. 

Weight 
of  KNOa 
used. 

Gravimet- 
ric 
method. 

Volumetric  method. 

Weight 
of  KNO, 
found. 

Reading 
of  nitrom- 
eter (N). 

Weight 
of  KNO, 
found. 

1 
2 
3 
4 
5 
6 

c.  c. 
100 
100 
100 
100 
100 
100 

Grams. 
1.0000 
1.0000 
ol.OOOO 
al.OOOO 
bl.OOOO 
«>  1.0000 

Grams. 
0.9994 

Grams. 

13.92 

1.0036 

.9997 

13.92 

1.0036 

1.0004 

13.93 

1.0043 

"  Two  one-hundredths  gram  of  sugar  was  added  to  the  100  c.  c.  of  nitrate  solution. 

*  Two  one-hundredths  gram  of  sodium  chloride  was  added  to  the  100  c.  c.  of  nitrate  solution. 

EXTRACTION    WITH    ACID. 

As  already  pointed  out,  the  materials  most  commonly  used  as 
antacids  are  the  carbonates  of  calcium  or  magnesium  or  the  oxide  of 
zinc.  Frequently  ground  dolomite  is  used,  in  which  case  both  cal- 
cium and  magnesium  must  be  determined.  The  qualitative  exam- 
ination will  have  shown,  however,  what  acid-soluble  materials  are 
present. 


46  ANALYSIS   OF   BLACK   POWDER  AND   DYNAMITE. 

The  procedure  to  be  followed  in  making  the  acid  extraction  depends 
on  whether  or  not  starch  is  present  in  the  explosive.  In  either  case 
the  dried  and  weighed  residue  insoluble  in  water  is  used  for  the 
treatment  with  acid. 

In  the  absence  of  starch  a  simple  extraction  is  made  with  cold 
dilute  hydrochloric  acid  (1:10),  100  c.  c.  being  drawn  through  the 
sample  in  the  crucible  in  small  successive  portions,  as  described 
under  "Extraction  with  water"  (p.  43).  Several  portions  of  water 
are  then  drawn  through  to  wash  out  the  acid,  and  the  crucible  with 
the  insoluble  residue  is  dried  as  before  for  five  hours  at  95  to  100°  C. 
It  is  sufficiently  accurate  to  use  this  "loss-of-weight"  figure  as  the 
amount  of  antacid,  as  the  amount  of  organic  material  extracted 
from  the  wood  pulp  will  be  very  small,  but  if  greater  accuracy  is 
desired  a  quantitative  determination  of  the  dissolved  base  or  bases 
may  be  made  by  the  usual  gravimetric  methods 

DETERMINATION    OF   CALCIUM. 

Calcium  is  determined  as  follows :  An  excess  of  ammonium  hydrox- 
ide is  added  and  the  solution  boiled.  Any  precipitate  of  iron  or 
aluminum  hydroxides  may  be  filtered  off,  ignited,  and  weighed,  but 
the  amount  of  such  impurities  is  usually  so  small  that  it  may  be 
disregarded  and  calcium  precipitated  without  previous  filtration. 
Hot  ammonium-oxalate  solution  is  added  in  slight  excess  to  the 
boiling  solution  and  the  boiling  is  continued  for  a  short  time.  The 
precipitate  is  allowed  to  settle  completely,  and  then  is  filtered,  dried, 
and  weighed  as  CaC2O4,  or  is  ignited  and  weighed  as  CaO. 

DETERMINATION   OF  MAGNESIUM. 

Magnesium  is  determined  in  the  filtrate  from  the  calcium  deter- 
mination by  concentrating  to  about  100  c.  c.,  adding  an  excess  of  a 
solution  of  sodium  hydrogen  phosphate  to  the  hot  solution,  then  a 
large  excess  of  ammonium  hydroxide,  and  allowing  the  phosphate 
precipitate  to  separate  completely  by  standing  for  several  hours. 
The  precipitate  is  filtered  in  a  Gooch  crucible,  washed,  ignited,  and 
weighed  as  Mg2P2O7. 

DETERMINATION    OF   ZINC. 

Zinc  is  precipitated  with  Na2CO3  solution  as  carbonate,  ignited, 
and  weighed  as  ZnO.  If  ammonium  salts  are  present  the  zinc  is 
precipitated  with  H2S  as  ZnS,  the  ZnS  filtered  off,  redissolved,  and 
precipitated  as  carbonate.  The  determination  of  zinc  is  more  fully 
considered  in  the  discussion  of  ammonia  dynamites  on  page  58. 


DYNAMITE.  47 

DETERMINATION   OF   STARCH. 

When  starch  is  present  both  the  starch  and  the  antacid  are  removed 
in  one  operation  by  boiling  with  dilute  acid,  whereby  the  starch  is 
rendered  soluble  by  conversion  to  dextrin.  In  carrying  out  this 
process  the  material  in  the  crucible  is  moistened  with  water  and 
completely  transferred  with  a  spatula,  or  by  washing  with  a  stream 
of  water  from  a  wash  bottle,  into  a  beaker  of  about  500  c.  c.  capacity. 
If  a  Gooch  crucible  is  used  the  asbestos  is  removed  with  the  residue 
and  the  clean  crucible  dried  and  weighed.  From  the  original  weight  of 
the  crucible  plus  the  asbestos  the  weight  of  the  asbestos  is  ascertained 
and  deducted  from  the  final  weight  of  dried  residue  remaining  after 
hydrolysis.  The  volume  of  water  in  the  beaker  is  made  up  to  about 
L^n  c.  c.,  and  about  3  c.  c.  hydrochloric  acid  (specific  gravity  1.2)  is 
added,  and  the  mixture  is  stirred  and  brought  to  boiling  over  a 
burner.  Boiling  is  continued  until  the  starch  is  entirely  hydrolized, 
a  drop  of  the  acid  mixture  being  tested  from  time  to  time  on  a  spot 
plate  with  a  solution  of  iodine  in  potassium  iodide  until  a  blue  color- 
ation is  no  longer  obtained.  Longer  boiling  will  only  result  in  loss 
of  extractive  material  from  the  wood  pulp. 

The  boiled  material  is  then  at  once  filtered  through  a  fresh  crucible 
or  through  the  original  porous  crucible,  if  such  was  used,  washed 
several  times  with  water,  dried  as  before,  and  weighed.  If  the 
figures  representing  the  weight  include  the  weight  of  the  asbestos  mat 
from  a  Gooch  crucible,  the  proper  correction  for  the  weight  of  the 
asbestos  is  made  as  noted  above. 

The  amount  of  antacid  contained  in  the  acid  filtrate  is  ascertained 
by  a  gravimetric  determination  as  previously  described. 

It  has  already  been  noted  (p.  44)  that  small  amounts  of  soluble 
organic  material  (sugars,  dextrin,  etc.)  from  flour  or  other  cereal 
products  and  extract  from  the  wood  pulp  will  be  found  in  the  water 
solution.  In  summarizing  the  results  of  analysis  it  is  of  course 
impossible  to  know  what  portion  of  such  extracted  organic  material 
constituted  part  of  the  flour  and  what  portion  should  properly  be 
added  to  the  wood  pulp.  Similarly,  the  organic  material  dissolved 
during  the  acid  hydrolysis  includes  not  only  such  portions  of  the 
grain  as  starch  and  gluten  but  soluble  portions  of  the  wood  pulp. 

It  is  customary  in  quoting  the  results  of  analysis  to  include  all 
such  soluble  organic  material  from  both  water  and  acid  extractions 
under  the  term  " starch,"  and  the  insoluble  residue  is  designated 
as  "wood  pulp  and  crude  fiber."  In  other  words,  the  weight  of 
insoluble  residue  dried  at  100°  is  called  "wood  pulp  and  crude  fiber/' 
whereas  the  sum  of  this  constituent  and  of  the  ingredients  determined 
in  the  ether,  water,  and  acid  solutions,  deducted  from  the  weight  of 
original  sample,  is  called  "starch." 


48 


ANALYSIS   OF   BLACK   POWDER  AND   DYNAMITE. 


In  the  case  of  a  dynamite  which  contains  no  cereal  product,  the 
sum  of  the  determined  ingredients  deducted  from  the  weight  of 
original  sample  is  taken  as  the  amount  of  wood  pulp  present  and 
includes  the  material  extracted  from  the  pulp  by  the  water  and  acid 
treatment  as  well  as  the  insoluble  residue  found  by  direct  weight. 

The  actual  amounts  of  wood  pulp  and  of  cereal  products  added  in 
manufacture  can  not  therefore  be  definitely  determined,  since  por- 
tions of  each  will  be  found  in  the  ether,  the  water,  and  the  acid 
extractions  as  well  as  in  the  insoluble  residue. 

In  order  to  determine  to  what  extent  the  wood  pulp  hi  a  dynamite 
is  affected  by  the  various  extractions,  etc.,  necessary  hi  the  course 
of  analysis  of  the  dynamite,  dried  samples  of  various  grades  of  pulp 
were  submitted  to  the  treatment  through  which  the  insoluble  wood 
pulp  residue  in  a  sample  of  dynamite  had  passed. 

Samples  of  2  to  3  grams  of  wood  pulp  were  weighed  in  Gooch 
crucibles,  dried  to  constant  weight,  and  extracted  successively  with 
ether,  water,  and  cold  hydrochloric  acid  (1 :10),  and  then  boiled  for  15 
minutes  with  dilute  hydrochloric  acid  (1 :100).  The  latter  treatment 
would  be  necessary  if  starch  were  present  with  the  wood  pulp  in  an 
explosive.  After  each  operation  the  sample  was  dried  five  hours  at 
100°,  and  the  loss  of  weight  was  determined.  The  results  were  as 

follows: 

Results  of  analyses  of  wood  pulp. 


Loss  01 

weight  (per 

cent  of  dry  s 

ample.) 

Sample 
No. 

Extraction 
with  ether. 

Extraction 
with  cold 
water. 

Extraction 
with  cold 
HC1(1:10). 

Boiling 
with  HC1 
(1:100) 

of  insol- 
uble 
residua. 

1  
2  
3  

4. 

2.66 
2.78 
2.09 
1.95 

2.57 
2.89 
2.23 
2.84 

1.41 
.42 
.53 
1.03 

5.91 
1.75 
3.93 
4.83 

87.45 
92.16 
91.22 
89.35 

These  experiments  show  that  the  final  insoluble  residue  that  is 
weighed  as  wood  pulp  may  be  only  about  90  per  cent  of  the  amount 
of  dry  wood  pulp  actually  present  in  the  dynamite.  A  part  of  the 
loss  is  determined  as  rosin  in  the  ether  extract,  and  the  portions 
extracted  with  water  and  hot  acid  are  calculated  as  starch  (if  starch 
has  been  determined).  When  starch  is  not  present  the  error  in  the 
determination  of  pulp  is  much  less  as  the  boiling-acid  treatment  is 
dispensed  with.  The  analysis  can  then  be  made  accurate  by  direct 
determination  of  the  water-soluble  nitrate  and  of  the  antacid  as 
described  above,  and  the  amount  of  wood  pulp  can  be  found  by 
subtracting  the  sum  of  the  percentages  of  moisture,  nitroglycerin, 
alkaline  nitrate,  and  antacid  from  100  per  cent.  This  amount  will 
be  in  excess  of  the  percentage  of  insoluble  residue  found,  according 
to  the  amounts  of  pulp  extracted  by  the  water  and  acid. 


DYNAMITE.  49 

EXAMINATION   OF    INSOLUBLE    RESIDUE. 
DETERMINATION    OP   WOOD  PULP,    KTO. 

The  residue  that  remains  after  the  ether  extraction,  the  water  ex- 
traction, and  the  extraction  with  dilute  acid  is  usually  a  mixture  of 
wood  pulp,  sawdust,  or  other  form  of  cellulose  or  lignin.  When  corn 
meal,  flour,  middlings,  bran,  etc.,  are  present  hi  the  dynamite,  the  resi- 
due will  contain  the  nonstarchy  portions  of  these  materials,  either  free 
or  mixed  with  wood  pulp.  In  general,  ordinary  dynamite  contains 
wood  pulp  alone  as  the  absorbent,  but  low-freezing  dynamites  and 
"straight"  dynamites  containing  less  than  40  per  cent  of  nitro- 
glycerin  often  contain  considerable  quantities  of  corn  meal,  wheat 
middlings,  or  low-grade  flour. 

Infusorial  earth  was  formerly  much  used  as  an  absorbent  for  nitro- 
glycerin,  but  in  recent  years  it  has  seldom  been  so  used  in  this  coun- 
try, having  been  almost  entirely  replaced  by  an  active  base  or  dope. 

If  the  hydrochloric  acid  has  not  been  thoroughly  washed  from  the 
insoluble  residue,  the  wood  pulp  will  considerably  darken  in  color 
during  the  drying  process.  From  its  physical  structure,  as  observed 
without  magnification,  or  with  a  small  lens,  much  information  may 
be  gained  in  regard  to  the  probable  composition  of  the  insoluble 
residue,  but  in  all  cases  the  examination  is  best  made  under  the 
microscope,  with  a  low-power  objective,  one  of  32-mm.  focus  being 
suitable.  One  of  the  duplicate  samples  of  insoluble  residue  is  used 
for  microscopic  and  chemical  examination,  and  one  for  the  deter- 
mination of  ash.  A  small  amount  of  the  sample  which  is  to  be  used 
for  microscopic  and  chemical  examination  is  removed  from  the 
crucible,  placed  upon  a  microscope  slide,  and  moistened  with  one 
or  two  drops  of  water.  By  means  of  a  platinum  needle  the  material 
is  then  carefully  spread  out,  but  no  cover  glass  is  used.  Wood 
pulp,  the  most  common  constituent  in  the  residue  of  ordinary  dyna- 
mite, will  be  seen  as  separate  fibers  or  bunches  of  fibers  of  very 
characteristic  appearance. 

In  Plate  IV,  A  and  B,  wood  pulp  of  different  grades  is  illustrated, 
and  the  characteristic  appearance  of  sawdust  or  dust  from  certain 
types  of  woodworking  machinery  is  shown  in  Plate  IV,  C.  The 
bundles  or  clusters  of  fibers  are  characteristic  of  such  materials. 
Typical  samples  of  infusorial  earth  (kieselguhr)  are  shown  in  Plate 
IV,  D  and  E.  It  should  be  noted  that,  as  plainly  shown  in  the  figures, 
widely  differing  types  of  infusorial  earth  exist,  forms  of  organisms 
appearing  hi  one  sample  which  will  not  be  found  in  another.  The 
general  appearance  of  shell  remains  is  a  definite  indication  of  the 
presence  of  diatomaceous  or  infusorial  earth.  The  sample  shown 
in  Plate  IV,  D,  was  obtained,  through  the  courtesy  of  Dr.  G.  P. 
67709°— Bull.  51—] 


50  ANALYSIS  OF  BLACK  POWDEE  AND  DYNAMITE. 

Merrill,  from  the  National  Museum,  Washington,  D.  C.  (Specimen 
No.  6555,  from  Cornwallis,  Nova  Scotia.) 

The  appearance  of  the  "  husks "  or  crude  fiber  from  coarse  wheat 
flour  (middlings),  after  hydrolysis  of  the  starch,  is  shown  in  Plate 
IV,  F;  the  cellular  structure  of  the  irregularly  shaped  particles  of 
fiber  is  readily  seen. 

A  and  B,  Plate  V,  represent  cellulose  (cotton)  and  nitrocellulose, 
respectively.  These  two  materials  can  not  be  distinguished  from 
each  other  by  microscopic  examination  in  ordinary  light,  but  in 
polarized  light  a  decided  difference  is  noted,  the  unnitrated  fibers 
appearing  in  brilliant  colors  and  the  nitrated  fibers  dark. 

In  the  case  of  the  presence  of  cereal  products  it  is  often  of  value  to 
make  a  microscopic  examination  of  the  residue  insoluble  in  water 
before  hydrolysis  of  the  starch.  In  Plate  V,  C,  D,  and  E,  such 
materials  are  shown.  C  represents  ordinary  fine  wheat  flour;  D, 
wheat  flour  mixed  with  wood  pulp;  E,  coarse  wheat  flour  or  mid- 
dlings; and  F,  corn  meal.  Characteristic  differences  in  the  appear- 
ance of  the  starch  granules  of  wheat  and  corn  are  of  aid  in  identifying 
these  cereals,  the  wheat  starch  granules  being  in  general  well  rounded 
or  oval,  whereas  the  cornstarch  granules  are  almost  always  dis- 
tinctly polygonal  in  shape. 

DETERMINATION    OF  ASH. 

The  remaining  sample  of  residue  from  acid  extraction  is  used  for 
the  determination  of  ash,  and  may  be  either  incinerated  in  the  cruci- 
ble that  has  been  used  for  extraction,  or  the  residue,  together  with  the 
asbestos  mat,  may  be  removed  to  a  platinum  crucible  and  ignited ; 
in  this  case  there  is  subtracted  from  the  ash  the  known  weight  of 
asbestos  present  in  the  mat.  The  ash  of  an  ordinary  dynamite,  con- 
taming  only  wood  pulp,  sawdust,  or  corn  meal  as  absorbents,  will 
seldom  amount  to  more  than  0.20  per  cent.  When  the  amount  of  ash 
present  is  as  much  as  0.5  per  cent  the  ash  should  in  all  cases  be 
examined  under  the  microscope  to  determine  the  possible  presence 
of  infusorial  earth  or  other  inorganic  material  (pulverized  glass,  sand, 
etc.),  provided  the  presence  of  these  materials  has  not  already  been 
detected  by  the  microscopic  examination.  A  high  ash  content  may 
also  indicate  that  either  the  water  or  acid  extractions  have  not  been 
complete.  In  this  respect  the  ash  determination  may  be  regarded 
as  a  check  on  the  analysis. 

VARIATIONS    DUE   TO   METHOD   OF   ANALYSIS. 

In  order  to  ascertain  to  what  extent  the  results  of  analysis  of  a 
dynamite  would  be  effected  by  variations  in  the  method  of  analysis, 
uniform  samples  of  a  45  per  cent  dynamite  were  submitted  to  the 
laboratories  of  1 1  explosives  works,  with  the  request  that  analyses  be 


BUREAU   OF   MINES 


BULLETIN    51      PLATE   IV 


A.     WOOD  PULP  NO.   1    (X  50). 


C.     SAWDUST  (X  25). 


'**£*  ' 


W*®& 


E.     INFUSORIAL  EARTH  NO.  2  (X  150). 


B.     WOOD  PULP  NO.  2  (X  50). 


O 


\   •    o 


' 


D.     INFUSORIAL  EARTH  NO.  1   (X  150). 


VJ 

JT 

1*. 

c 
.  ^ 


F.     CRUDE  FIBER  FROM  WHEAT  MID 
DLINGS  (X  25) 


DYNAMITE. 


51 


made  by  the  methods  regularly  in  use  in  each  laboratory  and  results 
reported,  together  with  brief  notes  as  to  the  method  used. 

The  samples  were  prepared  as  follows:  Fifty  cartridges  of  a  lot  of 
45  per  cent  dynamite  were  opened,  about  two- thirds  of  each  cartridge 
removed  (the  ends  being  rejected),  and  broken  up  finely  in  a  porce- 
lain dish  by  means  of  a  horn  spoon.  All  of  these  portions  were  then 
mixed  together  very  thoroughly  in  a  large  porcelain  dish.  From  this 
uniform  mixture  about  20  sample  bottles  (150  c.  c.  capacity)  were 
filled,  the  contents  of  each  bottle  then  being  emptied  out  separately 
into  a  dish,  carefully  mixed  again,  and  replaced  in  the  bottle.  Each 
sample  represented  about  150  grams. 

Eleven  of  these  samples  were  sent  to  different  laboratories,  as  noted 
above,  and  seven  of  them  analyzed  in  the  bureau's  explosives  chemi- 
cal laboratory  by  different  analysts.  Careful  instructions  were  sent 
with  each  sample,  that,  in  order  to  compensate  for  any  segregation 
occurring  in  shipment,  the  entire  sample  should  be  thoroughly  mixed 
before  analysis. 

The  results  of  the  analyses  of  these  samples  are  shown  in  the  fol- 
lowing table: 

Analyses  of  uniform  samples  of  dynamite. 


1 

2 

3 

4 

5 

I 

7 

Sample 
No 

Moisture. 

Nitro- 
glycerin. 

Potas- 
sium ni- 
trate. 

Calcium 
carbon- 
ate. 

Wood 
pulp. 

Nitroglycerin. 

Bv  direct 
weighing. 

By  ni- 
trometer. 

A 
B 
C 
D 
E 
Fa 
r, 
H 
J 
Kb 
L 
M 
N 
0 
PI 
P2 
P3 
Q 

1.21 
.89 
.99 
.91 
1.05 
1.02 
.41 
1.35 
1.22 

43.90 
44.99 
44.77 
45.25 
44.52 
42.29 
44.91 
44.86 
44.98 

39.14 
38.40 
38.75 
38.62 
38.05 
41.02 
39.04 
38.09 
38.48 

1.02 
1.15 
1.06 
.98 
1.28 
1.15 
1.12 
1.28 
.99 

14.73 
14.57 
14.59 
14.24 
15.10 
14.52 
14.  52 
14.42 
14.37 

1.60 
1.00 
1.19 
1.15 
1.04 
1.26 
.98 
1.18 

44.50 
45.70 
45.50 
45.48 
45.35 
45.22 
45.24 
45.42 

37.40 
37.57 
37.54 
37.69 
37.66 
37.33 
37.87 
37.60 

1.00 
1.17 
.15 
.16 
.10 
.20 
.21 
.19 

15.50 
14.56 
14.62 
14.52 
14.85 
14.88 
14.70 
14.61 

45.87 
45.31 

45.22 
45.17 

45.41 

45.14 

«  The  remarkable  difference  noted  in  the  analysis  of  this  sample  as  compared  with  all  other  samples,  is 
due  to  the  fact  that,  through  misunderstanding,  this  sample  was  not  mixed  on  being  received.  After 
several  analyses  had  been  made  with  widely  varving  results,  the  remainder  of  the  sample  was  mixed  by 
rubbing  through  sieves.  This  treatment  probably  resulted  in  considerable  loss  of  nitroglycerin.  Sample 
F  is  there  fore  not  considered  in  the  discussion  of  results. 

*  No  report  received. 

Samples  A  to  L  were  analyzed  in  the  laboratories  of  various  powder 
companies  and  samples  M  to  Q  in  the  bureau's  laboratory;  P2  and 
P3  were  analyzed  by  men  under  instruction,  not  members  of  the 
laboratory  force  of  the  bureau. 


52  ANALYSIS    OF   BLACK   POWDER  AND   DYNAMITE. 

DISCUSSION    OF   ANALYSES. 

MOISTURE. 

The  methods  employed  were  as  follows : 

Samples  E,  J,  and  M  to  Q,  inclusive — 3  grams  desiccated  on  watch 
glass  over  H2SO4  for  3  days  (0.98-1.26  per  cent). 

Sample  A — 6  to  10  grams  on  watch  glass,  3  days  over  H2SO4 
(1.21  per  cent). 

Sample  B — 3  grams  on  watch  glass,  2  days  over  CaCl2  (0.89  per 
cent) . 

Sample  D — 6  grams  on  watch  glass,  24  hours  over  H2SO4  in  vac- 
uum (0.91  per  cent). 

Sample  C — 2  grams  on  watch  glass,  24  hours  over  H2SO4,  15  inches 
vacuum  (0.99  per  cent). 

Sample  H — 5  grams  in  Gooch  crucible,  48  hours  over  H2SO4  at 
40°  C.  (1.35  percent). 

Sample  G — 10  grams  in  4-ounce  bottle,  dry- air  current  passing 
over  surface  of  sample  for  24  hours  (0.41  per  cent). 

Sample  L — 10  grams  in  drying  tube,  dry-air  current  passing  through 
sample  for  24  hours  (1.60  per  cent). 

It  is  noted  that  desiccation  on  a  watch  glass  over  H2SO4  for  three 
days  gave  only  0.3  per  cent  maximum  variation,  results  obtained 
with  the  aid  of  vacuum  for  24  hours  being  a  little  low.  Two  days 
over  CaClj  gave  low  results.  High  results  were  obtained  by  desic- 
cating at  40°  C.  and  by  passing  dry  air  through  the  sample,  from 
loss  of  nitroglycerin  under  these  conditions.  Passing  dry  air  over 
the  surface  of  the  sample  gave  low  results,  as  might  be  expected. 


NITROGLYCERIN. 


The  results  obtained  in  the  bureau's  laboratory  with  samples  M  to 
Q  varied  from  45.22  to  45.70  per  cent.  Samples  of  5  to  10  grams  in 
Gooch  crucibles  were  extracted  for  one  hour  with  U.  S.  P.  ether  (96 
per  cent)  in  the  Wiley  apparatus  and  the  residues  dried  five  hours 
at  100°  C.  The  loss  in  weight  minus  the  moisture  previously  deter- 
mined was  taken  as  the  nitroglycerin  content.  Samples  B,  E,  and  J 
were  analyzed  in  the  same  manner,  giving  results  from  44.52  to 
44.99  per  cent.  Samples  A,  C,  D,  G,  and  L  were  extracted  with 
ether  by  means  of  suction,  7  to  10  grams  of  sample  being  treated 
with  five  or  six  successive  portions  of  ether  (amounts  varying  from 
50  to  120  c.  c.).  Samples  A,  C,  and  D  were  dried  to  constant  weight 
in  steam  ovens  after  extracting  (the  time  of  drying  not  noted);  G 
was  dried  at  100°  to  105°,  and  L  for  two  hours  at  95°.  The  results 
varied  from  43.90  to  45.25  per  cent.  The  results  obtained  in  the 
bureau's  laboratory  (45.22  and  45.70  per  cent)  are  uniformly  higher 
than  those  obtained  in  other  laboratories  (43.90  to  45.25  per  cent). 


BUREAU    OF   MINES 


BULLETIN   51       PLATE   V 


.4.     CELLULOSE  (COTTON)   (X  50 1 


B.     NITROCELLULOSE   (X  50). 


C.     WHEAT  FLOUR  (FINE)   (X  50) 


D.     WHEAT  FLOUR  (FINE)  AND  WOOD 
PULP  (X  50). 


WHEAT  FLOUR  (MIDDLINGS)   (X  50). 


F.     CORN  MEAL  (X  50). 


DYNAMITE.  53 

Nitrometer  determinations  on  three  samples  (column  7)  showed  the 
true  nitroglycerin  content  of  the  evaporated  ether  extracts  to  be 
approximately  45.2  per  cent. 

No  explanation  can  be  given  for  the  large  number  of  results  in 
which  the  amounts  of  nitroglycerin  found  are  uniformly  low,  except 
failure  to  observe  one  or  more  of  the  following  precautions:  (1)  The 
extraction  must  be  complete;  (2)  the  residue  must  be  dried  to  con- 
>tant  weight  at  a  temperature  of  about  100°  C.;  (3)  the  dried  resi- 
due must  be  cooled  in  an  efficient  desiccator  and  weighed  as  soon  as 
cooled. 

POTASSIUM   NITRATE. 

The  results  obtained  in  the  bureau's  laboratory  varied  from  37.33 
to  37.87  per  cent.  The  determination  was  made  by  extracting  the 
residue  insoluble  in  ether  with  about  200  c.  c.  of  water,  and  deter- 
mining the  nitrate  hi  an  aliquot  part  of  the  water  solution  by  evap- 
oration, as  described  on  page  44.  No  correction  was  made  for  traces 
of  chlorides,  etc.,  in  the  solution.  The  determination  on  sample  H 
was  made  in  the  same  manner,  giving  38.09  per  cent,  while  on  sample 
L  an  aliquot  portion  of  the  water  extract  was  analyzed  hi  the  nitro- 
meter with  a  result  of  37.40  per  cent.  All  the  remaining  samples 
were  extracted  with  water,  the  insoluble  residues  dried  at  about  100C°. 
and  weighed,  the  loss  of  weight  being  regarded  as  potassium  nitrate. 
This  method  gave  high  results  (38.05  to  39.14  per  cent)  owing  to  the 
water-soluble  organic  matter  extracted  from  the  wood  pulp. 

CALCIUM  CARBONATE. 

In  samples  L  to  Q  the  calcium  carbonate  was  determined  gravi- 
metrically  in  the  dilute-acid  extract;  in  samples  C  and  D  by  direct 
titration  of  the  residue  insoluble  in  water,  or  of  the  ash  left  after 
burning  off  the  pulp;  in  A,  B,  E,  and  J  the  loss  of  weight  on  extrac- 
tion with  dilute  acid  was  considered  as  calcium  carbonate,  while  in 
G  and  H  the  ash  was  assumed  to  be  entirely  calcium  carbonate.  The 
variations  are  of  minor  importance  and  no  conclusions  can  be  drawn 
from  the  results. 

WOOD   PULP. 

Variations  in  the  method  of  determining  the  potassium  nitrate 
influence  the  proportion  of  wood  pulp  reported.  When  the  loss  of 
weight  on  extracting  with  water  is  assumed  to  be  entirely  potassium 
nitrate,  in  spite  of  the  fact  that  it  contains  considerable  organic 
matter  extracted  with  the  wood  pulp,  the  proportion  of  wood  pulp 
found  will  be  lower  than  if  the  nitrate  is  determined  by  a  direct 
method  and  the  wood  pulp  by  difference.  The  percentage  of  wood 
pulp  being  found  by  subtracting  the  sum  of  all  other  constituents 
from  100  per  cent,  no  comparison  of  results  is  possible. 


GELATIN    DYNAMITE. 


Unlike  ordinary  dynamite,  which  contains  nitroglycerin  absorbed 
in  a  porous  material,  gelatin  dynamite  contains  nitroglycerin  com- 
bined with  nitrocellulose  to  form  a  plastic  solid.  When  nitroglycerin 
is  warmed  with  nitrocellulose  containing  about  12  per  cent  of  nitro- 
gen, the  nitroglycerin  dissolves  the  nitrocellulose,  and  a  thick,  vis- 
cous mass  is  produced  which  resumes  a  jelly-like  consistency  as  soon 
as  it  has  cooled.  When  as  little  as  3J  per  cent  of  nitrocotton  is  dis- 
solved in  nitroglycerin  at  60°,  the  material  should  form  a  jelly-like 
nonflowing  mass  when  cooled  to  ordinary  temperatures,  but  when 
smaller  amounts  of  nitrocellulose  are  used  the  viscosity  of  the  solu- 
tion becomes  less.  The  explosive  known  as  " blasting  gelatin" 
consists  of  about  93  to  90  per  cent  of  nitroglycerin  and  7  to  10  per 
cent  of  nitrocellulose,  and  is  a  translucent,  jelly-like  mass,  containing 
the  highest  percentage  of  nitroglycerin  used  in  any  solid  explosive. 

Any  explosive  containing  nitroglycerin  combined  with  nitrocellu- 
lose in  connection  with  an  active  base  consisting  of  a  nitrate  and 
combustible  material  is  termed  a  " gelatin  dynamite."  The  gelatin 
dynamites  have  many  properties  that  make  them  desirable  for  mining 
work,  their  greatest  advantage  being  that  they  are  almost  unaffected 
by  water. 

SAMPLING. 

The  coherent,  pasty,  doughlike  consistency  of  gelatin  dynamite 
renders  the  preparation  of  a  uniform  sample  much  more  difficult  than 
is  the  case  with  ordinary  dynamite. 

A  sample  is  prepared  from  one  or  more  cartridges  by  cutting  off 
portions  from  different  parts  of  each  stick;  these  portions  are  then 
cut  into  thin  pieces  and  broken  up  as  finely  as  possible  by  means  of  an 
aluminum  or  platinum  spatula.  The  use  of  a  steel  spatula  or  knife 
is  not  to  be  recommended.  The  sample  so  prepared  is  well  mixed 
and  bottled,  and  because  of  its  tendency  to  form  a  solid  mass  again 
on  standing,  it  should  be  analyzed  as  soon  as  possible  after  being 
prepared. 

The  ingredients  that  may  be  found  in  the  various  types  of  gelatin 
dynamite  are  nitroglycerin;  nitrocellulose;  sulphur;  rosin;  sodium, 
potassium,  or  ammonium  nitrate;  calcium  or  magnesium  carbonate; 
wood  pulp;  and  cereal  products. 

Moisture  is  determined  in  the  manner  previously  described. 
64 


GELATIN  DYNAMITE.  55 

The  extraction  with  ether  is  made  as  for  dynamite  except  that  ether 
distilled  over  sodium  (that  is,  ether  free  from  alcohol)  is  used  in  order 
to  avoid  the  partial  solution  of  the  nitrocellulose.  Nitrocellulose  is 
insoluble  in  pure  ether,  but  a  small  percentage  of  alcohol  present  as  an 
impurity  may  cause  the  solution  of  a  considerable  proportion  of  this 
constituent,  and  as  the  amount  of  nitrocellulose  is  usually  only  0.5  to 
2  per  cent  its  determination  should  be  accurate. 

The  ether  solution  con  taming  the  nitroglycerin,  sulphur,  and  rosin 
is  treated  in  the  manner  already  described,  and  the  water  extraction 
of  the  dried  and  weighed  insoluble  residue  is  made  in  the  usual  way. 

SULPHUR. 

If  the  percentage  of  sulphur  is  unusually  high,  or  if  the  extraction 
with  ether  has  not  been  continued  long  enough,  some  sulphur  may 
remain  in  the  dried  residue  left  after  water  extraction,  in  which  case 
an  additional  extraction  is  made  with  carbon  disulphide  in  the  Wiley 
apparatus,  the  same  method  as  described  for  the  ether  extraction  being 
used.  After  the  extraction  with  carbon  disulphide  has  been  made,  the 
crucibles  should  be  sucked  dry  and  the  carbon  disulphide  allowed  to 
evaporate  in  a  warm  place  before  the  crucibles  are  placed  in  the  oven, 
as  the  vapors  of  carbon  disulphide  are  very  inflammable  and  may 
ignite  in  the  oven.  The  crucibles  with  their  dried  residue  are  weighed 
and  the  loss  of  weight  considered  as  sulphur. 

The  extraction  with  water  is  next  made  as  before  described. 

NITROCELLULOSE. 

Nitrocellulose  is  now  removed  by  means  of  a  suitable  solvent. 
The  pyroxylin  cotton  usually  employed  as  a  gelatinizing  agent  is 
soluble  in  a  mixture  of  two  parts  ether  and  one  part  alcohol,  but  as 
all  grades  of  nitrocellulose  are  more  readily  soluble  in  acetone  than  in 
ether  alcohol  it  is  customary  to  use  acetone  as  the  solvent. 

The  extraction  with  acetone  is  made  by  separating  the  dry  residue 
from  the  crucible,  leaving  the  mat  intact  if  possible,  placing  the 
residue  in  a  small  beaker  and  covering  it  with  acetone.  The  mixture 
is  allowed  to  stand  for  three  to  four  hours,  with  frequent  stirring  to 
dissolve  completely  the  nitrocellulose,  and  is  then  filtered  through  the 
original  crucible,  washed  with  acetone,  dried  in  the  usual  manner,  and 
weighed.  The  loss  of  weight  represents  nitrocellulose  plus  a  small 
amount  of  extract  from  the  wood  pulp.  The  wood  pulp  extract  is 
usually  so  small  that  it  may  be  disregarded,  but  a  check  on  the  nitro- 
cellulose determination  may  be  made  by  evaporating  the  acetone 
solution  to  a  small  volume  (about  20  c.  c.),  and  diluting  gradually 
with  a  large  volume  of  hot  water  (about  100  c.  c.),  which  drives  off 
the  volatile  solvent,  precipitating  the  nitrocellulose  as  a  white  floc- 
culent  mass.  The  precipitate  is  then  filtered  off,  dried,  and  weighed 
as  nitrocellulose. 


56  ANALYSIS  OF  BLACK  POWDEK  AND  DYNAMITE. 

The  remainder  of  the  analysis  is  conducted  as  is  that  described 
for  straight  dynamite. 

Some  of  the  older  types  of  gelatin  dynamites  contained  small 
amounts  (1  to  2  per  cent)  of  paraffin,  but  this  is  an  unusual  ingredient 
and  is  more  frequently  found  in  ammonia  dynamite.  (See  p.  57.) 

Ammonia  gelatin  dynamite  is  a  type  that  has  of  recent  years 
assumed  commercial  importance.  It  differs  from  ordinary  gelatin 
dynamite  in  the  fact  that  it  contains  ammonium  nitrate  in  addition 
to  the  usual  constituents  of  the  former.  As  in  the  ammonia  dyna- 
mites, discussed  later,  so  here  the  ammonium  nitrate  is  usually  pre- 
viously coated  with  vaseline,  paraffin,  or  other  waterproofing  mate- 
rial, and  is  neutralized  with  zinc  oxide. 

In  the  analysis  of  gelatin  dynamite  it  should  be  remembered  that 
trade  custom  has  led  to  an  erroneous  system  of  designating  the 
strength  of  explosives  of  this  class.  Thus  a  gelatin  dynamite  con- 
taining about  30  to  33  per  cent  of  nitroglycerin  and  about  1  per  cent  of 
nitrocotton  is  called  a  "  40  per  cent ' '  strength  gelatin  dynamite.  This 
unfortunate  practice  undoubtedly  had  its  origin  in  the  fact  that,  as 
gelatin  dynamite  is  much  denser  than  ordinary  dynamite,  and  a 
greater  quantity  can  therefore  be  placed  in  a  hole,  it  was  assumed  to 
be  stronger.  Comparative  tests  indicate  that,  weight  for  weight, 
a  so-called  "40  per  cent' '  strength  gelatin  dynamite  containing  33  per 
cent  nitroglycerin  is  much  weaker  than  is  an  ordinary  "straight" 
dynamite  containing  40  per  cent  nitroglycerin. 


AMMONIA  DYNAMITE. 


The  usual  type  of  ammonia  dynamite  is  practically  a  "straight" 
dynamite  in  which  a  large  part  of  the  nitroglycerin  is  replaced  by 
ammonium  nitrate.  Sulphur  is  sometimes  a  constituent  of  this 
type  of  explosive,  and  frequently  the  wood  pulp  is  wholly  or  largely 
replaced  by  coarse  flour  or  middlings.  The  ammonium  nitrate  is 
generally  protected  from  hygroscopic  influence  by  a  coating  of  vaseline 
or  paraffin  and  is  neutralized  with  zinc  oxide.  These  ingredients  are 
added  to  the  ammonium  nitrate  in  the  course  of  its  manufacture 
while  the  crystals  of  the  ammonium  nitrate  are  still  hot. 

In  the  analysis  of  such  explosives  the  determination  of  moisture 
and  extractions  with  ether,  water,  and  acid  are  carried  out  as  pre- 
viously described.  An  additional  extraction  with  carbon  disulphide 
is  usually  necessary  in  order  to  remove  all  of  the  sulphur;  this  is  done 
after  the  water-soluble  salts  have  been  extracted. 

One  portion  of  the  ether  extract  is  used  for  the  determination  of 
nitroglycerin  in  the  nitrometer  and  the  other  for  the  determination 
of  the  sulphur  and  vaseline  or  paraffin. 

The  method  for  the  analysis  of  the  ether  extract  as  described  on 
pages  41  and  42  is  the  scheme  of  separation  followed  when  both  sulphur 
and  vaseline,  or  paraffin,  are  present  with  the  nitroglycerin,  although 
several  other  methods  are  applicable  and  give  reliable  results. 

The  nitroglycerin  may  be  destroyed  by  means  of  caustic  alkali, 
which  also  dissolves  any  resin  present;  the  solution  is  decanted 
from  the  residue  of  paraffin,  or  vaseline,  and  sulphur;  the  resin  is 
precipitated  with  hydrochloric  acid,  filtered,  dried,  and  weighed. 
The  residue  of  sulphur  and  paraffin  or  vaseline  is  treated  with  hot 
ammonium  sulphide  which  dissolves  the  sulphur;  this  solution  is 
cooled,  decanted,  and  the  vaseline  or  paraffin  adhering  to  the  beaker 
is  washed,  dried,  and  weighed.  The  weight  of  sulphur  is  found  by 
difference.0 

The  water  extract  contains  both  ammonium  and  sodium  nitrates, 
together  with  water-soluble  organic  material  from  the  flour  or  other 
absorbent.  If  zinc  oxide  has  been  used  as  the  antacid,  all  of  this 
component  will  generally  be  found  in  the  water  extract,  since  the 
small  amounts  used  are  readily  soluble  in  ammonium  nitrate  solutions. 

•  Gody,  L.,  Traite  theorique  et  pratique  des  matures  explosives,  1907,  pp.  388-389. 

57 


58  ANALYSIS  OF  BLACK  POWDER  AND  DYNAMITE. 

An  aliquot  part  of  the  water  extract  is  evaporated  in  a  platinum  dish 
on  a  steam  bath,  the  ammonium  nitrate  volatilized,  and  the  organic 
matter  burned  off  by  careful  heating  over  a  burner.  A  little  nitric 
acid  is  added  to  oxidize  to  nitrate  any  nitrite  resulting  from  reduction, 
as  described  on  page  44.  In  heating  this  residue  care  must  be  taken 
to  avoid  decomposition  of  the  zinc  nitrate,  or  else  the  heating  should 
be  strong  enough  to  convert  it  entirely  to  zinc  oxide.  Either  of  the 
following  methods  may  be  used : 

(1)  The  residue,  after  evaporation  of  the  nitric  acid  on  the  steam 
bath,  is  dried  at  about  110°  to  120°,  and  weighed  as  NaNO3  and 
Zn(NO3)2.     This  residue  is  then  dissolved  in  water  and  the  zinc 
precipitated  with  sodium  carbonate,  filtered,  ignited,  and  weighed 
as  ZnO.     The  weight  of  NaNO3  and  Zn(NO3)2  minus  (2.33  times  the 
weight  of  ZnO)  equals  NaNO3. 

(2)  The  residue  obtained  as  above  is  heated  gently  over  a  burner 
until  the  evolution  of  oxides  of  nitrogen  from  the  decomposition  of  the 
zinc  nitrate  has  ceased,  care  being  taken  that  the  temperature  is  not 
high  enough  to  cause  a  loss  of  sodium  nitrate.     The  residue  is  now 
weighed  as  NaNO3  plus  ZnO,  then  treated  with  water  to  dissolve  the 
NaN03 ;  the  ZnO  is  filtered  on  a  Gooch  crucible,  ignited,  and  weighed 
as  ZnO,  the  NaN03  being  found  by  difference  from  the  combined 
weight.     The  filtrate  containing  the  sodium  nitrate  should  be  tested 
with  ammonium  sulphide  to  assure  that  the  zinc  has  been  entirely 
converted  to  insoluble  zinc  oxide. 

Zinc  may  be  determined  in  a  separate  portion  of  the  water  extract 
by  adding  ammonia,  precipitating  with  hydrogen  sulphide,  and 
filtering  off  the  precipitated  zinc  sulphide.  The  precipitate  is 
washed  and,  without  drying,  dissolved  in  a  small  amount  of  nitric 
acid,  and  evaporated  to  dryness.  Any  free  sulphur  is  thus  oxidized. 
The  residue  is  treated  with  a  little  sulphuric  acid  and  again  evaporated 
to  dryness  over  a  burner  at  a  dull-red  heat  until  the  free  acid  has  been 
volatilized.  Little,  if  any,  decomposition  of  the  zinc  sulphate 
results  from  this  heating.  The  treatment  with  sulphuric  acid  and 
heating  should  be  repeated  until  a  constant  weight  of  ZnSO4  is 
obtained.  This  method  is  convenient  and  has  been  found  to  check 
well  with  the  methods  described  above. 

Ammonium  nitrate  is  determined  directly  with  a  separate  portion 
of  the  water  extract  by  the  usual  method  of  distilling  from  a  solution 
made  strongly  alkaline  with  KOH,  collecting  the  distillate  in  a 
known  volume  of  standard  H2SO4,  and  titrating  the  excess  of  acid 
with  standard  alkali,  cochineal  being  used  as  an  indicator. 

In  regard  to  the  determination  of  ammonium  nitrate,  the  possible 
effects  of  several  influencing  factors  have  been  investigated.  Stillman 
and  Austin  state  that  ammonium  nitrate  is  slightly  soluble  in  ether,0 

a  Kast,  H..  Anleitung  zur  chemischen  und  physikalischen  Untersuchungen  der  Spreng-  und  Ziindstoffe, 
1909,  p.  980. 


AMMONIA   DYNAMITE. 


59 


and  several  other  authors  have  noted  that  correction  should  be  made 
for  this  solubility. 

Ten-gram  samples  of  pure  ammonium  nitrate  were  desiccated  to 
constant  weight  over  sulphuric  acid  and  were  extracted  with  U.  S.  P. 
(96  per  cent)  ether  for  one  hour  in  the  Wiley  apparatus.  On  drying 
to  constant  weight  in  vacuum  desiccators  a  maximum  loss  of  only 
0.10  per  cent  was  noted.  Additional  drying  of  the  same  samples 
at  70°  for  18  hours  caused  a  further  loss  of  0.07  to  0.15  per  cent. 
On  continuing  the  drying  at  90°  to  100°  further  losses  calculated  as 
percentages  of  the  original  sample  were  as  follows: 

Loss  in  weight  of  ammonium  nitrate  dried  at  90°  to  100°. 


Time  of 
drying. 

Total  loss,  per  cent. 

Sample  1. 

Sample  2. 

Hours. 
2 
5 
24 
120 
240 

0.03 
.03 
.07 
.33 
.62 

0.04 
.05 
.11 
.39 
.67 

The  above-mentioned  experiments  show  that  the  loss  of  pure 
ammonium  nitrate  by  the  ether  extraction  and  by  subsequent  drying 
for  several  hours  at  70°  or  100°  is  very  slight — not  over  0.25  per  cent. 

That  the  loss  on  drying  depends  on  the  surface  exposed  was  shown . 
by  drying,  at  90°  to  100°,  5-gram  samples  spread  on  3-inch  watch 
glasses.  The  losses  were  as  follows: 

Loss  in  weight  of  ammonium  nitrate  dried  on  3-inch  watch  glasses  at  90°  to  100°  C. 


Time  of 
drying. 

Loss  of  weight,  per  cent. 

Sample  1. 

Sample  2. 

Hours. 
5 
24 
48 
120 
168 

0.34 
.88 
2.03 
6.11 
7.09 

0.33 
.98 
1.57 
4.64 
5.84 

In  this  case  the  much  greater  surface  of  samples  exposed  caused  a 
much  more  rapid  volatilization. 

In  the  analysis  of  an  explosive  containing  zinc  oxide,  it  must  be 
remembered  that  in  addition  to  mere  volatilization  there  is  possible 
still  further  loss  from  the  decomposing  action  of  the  ZnO  on  the 
ammonium  nitrate.  This  is  shown  by  the  following  experiment: 
Two  10-gram  samples  of  ammonium  nitrate  were  ground  in  a  mortar, 
0.5  gram  zinc  oxide  being  well  mixed  with  one  sample.  The  two 
samples  were  then  placed  in  crucibles  and  heated  at  100°.  The 
losses  in  weight  are  given  in  the  table  following: 


60  ANALYSIS   OF  BLACK  POWDEE  AND  DYNAMITE. 

Loss  in  weight  of  ammonium  nitrate  with  and  without  zinc  oxide  on  heating  at  100* 


Time. 

Loss  in  weight,  per  cent. 

Ammo- 
nium ni- 
trate. 

Ammo- 
nium ni- 
trate plus 
5  per  cent 
of  zinc 
oxide. 

Hours. 
2 
18 
48 

0.02 
.11 
.16 

0.61 
1.07 
1.13 

The  effect  of  too  high  temperature  of  drying  is  shown  more  clearly 
in  the  following  experiments  with  an  ammonium  nitrate  explosive  of 
the  "permissible"  class,  containing  nitroglycerin.  The  explosive 
contained  about  75  per  cent  of  NH4NO3  and  1.4  per  cent  of  ZnO. 
Six  10-gram  samples  were  extracted  with  ether  in  the  usual  manner 
to  remove  the  nitroglycerin.  Two  of  the  extracted  samples  were 
dried  over  night  at  100°  C.,  two  over  night  at  70°  C.,  and  two  for  24 
hours  in  vacuum  desiccators  to  constant  weight.  The  samples  were 
then  extracted  with  water,  dried  five  hours  at  100°  C.,  and  the  loss 
in  weight  noted.  Ammonium  nitrate  was  determined  in  the  water 
solutions  by  the  distillation  method  previously  described.  The 
results  are  tabulated  below: 

Effect  of  different  methods  of  drying  ammonium  nitrate  explosives  after  ether  extraction. 
[Determinations  by  J.  H.  Hunter.] 


Method  of  drying. 

Loss  of  weight,  per  cent. 

NH^NOs  in  water  solu- 
tion, per  cent. 

Ether  extraction. 

Water  extraction. 

High. 

Low. 

Mean. 

High. 

Low. 

Mean. 

High. 

Low. 

Mean. 

In  a  100°  oven  

13.48 
11.72 
11.68 

13.10 
11.64 
11.57 

13.29 
11.68 
11.63 

77.58 
79.29 
79.22 

77.23 

79.09 
79.11 

77.40 
79.19 
79.17 

71.76 

74.78 
75.20 

71.76 
74.90 
75.25 

In  a  70°  oven 

75.01 
75.31 

In  a  vacuum  desiccator  

These  results  show  clearly  that  drying  at  100°  after  extraction 
with  ether  causes  a  considerable  loss  of  ammonium  nitrate,  most 
of  the  loss  being  due  to  decomposition  of  the  nitrate  by  the  zinc 
oxide. 

The  sum  of  the  amounts  of  sodium  nitrate,  ammonium  nitrate, 
and  zinc  oxide  found  in  the  water  solution  will  be  less  than  the  total 
water  extract,  since  the  latter,  as  before  noted,  includes  water- 
soluble  organic  material  from  the  wood  pulp,  flour,  or  other  carbona- 
ceous absorbents.  This  organic  material  is  added  to  the  amount 
of  starch,  etc.,  removed  by  hydrolysis  and  reported  as  "starch,"  as 
has  been  noted  on  a  previous  page. 


LOW-FREEZING    DYNAMITE. 


Nitroglycerin  congeals  or  freezes  at  a  temperature  of  about  8°  C. 
(46°  F.),  and  as  nitroglycerin  in  the  frozen  condition  is  much  less 
sensitive  to  the  action  of  a  detonator  than  when  in  the  liquid  condi- 
tion, explosives  containing  frozen  nitroglycerin  usually  fail  to  explode 
when  attempts  are  made  to  use  them. 

As  the  outdoor  temperature  for  several  months  in  the  year  is  on 
the  average  below  the  temperature  at  which  nitroglycerin  explosives 
freeze,  many  efforts  have  been  made  to  prepare  low-freezing  explo- 
sives, which,  without  being  thawed,  may  be  used  at  temperatures 
lower  than  that  at  which  ordinary  nitroglycerin  explosives  are 
frozen.  Some  types  of  nonfreezing  explosives  contain  ammonium 
nitrate  mixed  with  nitrostarch,  nitro toluene,  or  similar  material,  but 
those  explosives  to  which  the  term  " low-freezing"  is  usually  applied 
contain  nitroglycerin  mixed  with  the  liquid  nitrotoluenes,  with 
crystalline  dinitrotoluene  or  trinitrotoluene,  with  the  nitrochlorhy- 
drins  or  other  materials,  it  having  been  shown,  for  example,  that 
20  per  cent  of  dinitrochlorhydrin  in  nitroglycerin  reduces  the  tem- 
perature at  which  the  mixture  will  freeze  to  about  — 12°  C.,°  and  by 
the  use  of  mixtures  of  nitroglycerin  and  dinitrotoluene  explosives 
are  prepared  which  may  be  used  at  temperatures  considerably  below 
0°C. 

Many  low-freezing  explosives  are  marked  with  the  designation 
"L.  F. "  upon  their  wrappers;  but  even  in  the  absence  of  this  notice 
of  the  nature  of  the  explosive  a  low-freezing  dynamite  may  frequently 
be  distinguished  by  the  odor  of  nitrotoluene,  or  by  the  color  test 
for  nitrosubstitution  compounds  made  on  the  ether  extract  as 
described  under  "Qualitative  examination,"  on  pages  17  and  18. 

DETERMINATION  OF  NITROSUBSTITUTION  COMPOUNDS. 

With  low-freezing  dynamites  the  methods  of  sampling  and  of 
determination  of  moisture  are  carried  out  in  the  manner  already 
outlined.  The  extraction  with  ether  is  also  made  in  the  usual 
manner,  and  one  of  the  samples  of  ether  extract  is  used,  as  outlined 
on  a  preceding  page,  for  the  determination  of  resins,  sulphur,  or 
other  ingredients.  The  other  sample  of  ether  extract  is  used  for 
the  determination  of  the  nitroglycerin  and  nitrosubstitution  products. 

•  Roewer,  F.  A.,  Proc.  6th  Int.  Cong.  App.  Chem.,  vol.  1, 1906,  p .  541. 

61 


62  ANALYSIS   OF  BLACK  POWDER  AND  DYNAMITE. 

So  far  as  is  known  by  the  writers,  no  satisfactory  method  has  yet 
been  found  for  the  direct  determination  of  nitrosubstitution  com- 
pounds in  the  presence  of  nitroglycerin.  The  analysis  of  such  mix- 
tures is  generally  made  by  determining  the  nitroglycerin  by  means 
of  the  nitrometer  (p.  35),  and  finding  the  amount  of  nitrosubstitu- 
tion compound  by  difference.  The  nitrosubstitution  compounds 
are  not  decomposed  in  the  nitrometer  as  are  the  nitric  esters. 

It  is  interesting  to  note,  however,  that  if  mononitro toluene  is 
present  the  amount  of  nitroglycerin  found  by  means  of  the  nitrom- 
eter does  not  represent  the  true  amount  of  this  ingredient  in  the 
mixture.  It  has  been  found  a  that  a  portion  of  the  nitric  acid 
liberated  from  the  nitroglycerin  by  the  action  of  the  sulphuric  acid 
used  in  the  determination  is  taken  up  by  the  mononitrotoluene  present, 
the  latter  becoming  quantitatively  nitrated  to  dinitro toluene. 
Thus,  if  the  amount  of  nitroglycerin  in  the  ether  extract  is  not  in 
excess  of  the  theoretical  amount  required  to  yield  sufficient  nitrogen 
to  convert  all  the  mononitrotoluene  to  dinitro  toluene,  no  evolution 
of  nitric  oxide  will  result.  In  other  words,  the  error  in  the  deter- 
mination of  nitroglycerin  is  equal  to  about  0.5530  gram  of  nitro- 
glycerin for  each  gram  of  mononitrotoluene  present.  Pure  crystalline 
dinitro  toluene  or  trinitrotoluene  was  found  to  have  no  effect  on  the 
determination,  and  the  same  was  found  to  be  true  of  the  so-called 
''liquid  trinitrotoluene."  "Liquid  dinitro  toluene/'  however,  causes 
an  error  amounting  to  0.0628  gram  of  nitroglycerin  for  each  gram 
of  the  nitrosubstitution  product.  This  error  was  shown  to  be  prob- 
ably due  to  the  presence  of  mononitrotoluene  in  the  liquid  dinitro- 
toluene. 

These  results  show  that  the  nitrometer  method  for  determination 
of  nitroglycerin  is  not  reliable  if  mononitrotoluene  is  present.  The 
latter  is,  however,  seldom  used  in  low-freezing  dynamites,  and  in  the 
case  of  the  more  commonly  used  liquid  dinitrotoluene,  the  resulting 
error  is  not  large.  For  example,  in  an  explosive  containing  25  per 
'cent  of  nitroglycerin  and  10  per  cent  of  liquid  'dinitrotoluene,  the 
error  in  the  determination  of  nitroglycerin  would  amount  to  0.628 
per  cent,  or  the  amount  of  nitroglycerin  found  would  be  24.37  per 
cent  instead  of  25  per  cent. 

Further  information  may  bo  gained  by  determining  the  total 
nitrogen  of  both  the  nitroglycerin  and  the  nitrosubstitution  com- 
pound by  a  modification  of  the  Kjeldahl  method  and  deducting 
the  nitrogen  of  the  nitroglycerin,  the  difference  being  the  nitrogen 
of  the  nitrosubstitution  compound.  From  this  nitrogen  the  amount 
of  the  latter  can  be  calculated.  This  method  is  of  value  only  if  the 

a  Storm,  C.G.,  The  effect  of  nitrotoluenes  on  the  determination  of  nitroglycerin  by  means  of  the  nitrom- 
eter, Proc.  8th  Int.  Cong.  App.  Chem.,  vol.  4, 1912,  p.  117. 


LOW-FREEZING   DYNAMITE.  63 

nitrosubstitution  compound  has  been  identified  by  the  preliminary 
examination. 

Another  method  for  the  determination  of  the  total  nitrogen  of 
such  mixtures,  as  well  as  the  ester  nitrogen,  is  that  of  Berl  and 
Jurrissen,0  in  which  a  so-called  " decomposition  flask"  is  used. 
By  means  of  sulphuric  acid  and  a  small  amount  of  mercury  in  a 
vacuum  the  decomposition  of  nitroglycerin  or  other  nitric  ester  is 
effected  and  the  resulting  volume  of  nitrogen  oxide  (NO)  measured. 
A  second  sample  of  the  mixture  is  treated  in  the  same  manner  after 
a  preliminary  oxidation  with  chromic  acid  and  sulphuric  acid, 
whereby  the  total  nitrogen  is  converted  to  nitrogen  oxide  (NO). 
The  difference  between  the  two  volumes  of  nitrogen  oxide  (NO) 
equals  that  resulting  from  the  nitrosubstitution  compound. 

The  remainder  of  the  analysis — the  extractions  with  water,  acid, 
etc. — is  conducted  in  the  manner  previously  described  and  should 
present  no  further  difficulties. 

«  Berl.  E..  and  Jurrissen,  A.  W.,  Uber  gasvolumetrische  Analyse  mit  dem  "Zersetzungskolben"  und 
die  Stiokstoffbestimmung  in  rauchschwachen  Pulvern.    Z«itschr.  angew.  Chem.,  vol.  23,  1910,  p.  241. 


GRANULATED    NITROGLYCERIN   POWDER. 


When  ordinary  dynamite  is  used  in  blasting  any  material  of  a 
consistency  resembling  that  of  earth  or  clay,  little  of  the  energy  of 
the  explosive  does  useful  work,  because  the  soft  and  compressible 
nature  of  the  material  blasted  allows  the  greater  part  of  the  energy 
of  the  explosive  to  be  used  in  compacting  the  material  and  in  pro- 
ducing a  cavity.  Consequently,  gunpowder  has  been  largely  used 
in  all  places  where  earth,  clay,  or  other  soft  material  was  to  be 
dislodged.  In  the  blasting  of  the  banks  of  railroad  cuts  there  are 
often  places  where  a  soft,  but  somewhat  consolidated  material,  inter- 
mediate between  earth  and  hard  rock,  has  to  be  blasted.  Such  a 
material  might  be  a  soft  shale,  for  example,  or  a  friable  and  easily 
crumbled  sandstone,  and  for  dislodging  it  neither  ordinary  blasting 
powder  nor  ordinary  dynamite  is  particularly  suitable.  In  the  year 
1876  E.  Judson  patented  an  explosive  consisting  of  a  low-grade  gun- 
powder made  by  heating  and  mixing  together  coal,  sulphur,  sodium 
nitrate,  etc.,  granulating  the  mixture,  and  then  coating  this  non- 
absorbent  granulated  dope  with  a  small  amount  of  nitroglycerin. 
The  proportion  of  nitroglycerin  used — often  as  little  as  5  per  cent — 
was  such  that  had  it  been  absorbed  by  the  grains  of  explosive  it 
would  not  have  been  capable  of  detonation,  but  by  remaining  wholly 
or  largely  upon  the  surface  of  the  grains  the  use  of  a  detonator 
brought  about  its  explosion  and  the  simultaneous  ignition  of  the 
gunpowder  base  which  it  covered.  Such  an  explosive,  as  a  result 
of  the  detonation  of  the  nitroglycerin,  produces  an  initial  blow 
sufficient  to  crack  and  fissure  the  partly  consolidated  material  in 
which  it  is  placed.  The  action  of  the  gunpowder  mixture  that 
forms  the  larger  part  of  the  explosive  so  heaves  and  moves  the 
broken-up  mass  as  to  make  easy  its  removal  with  steam  shovels. 

Granulated  nitroglycerin  powders,  or  " free-running"  explosives, 
have  been  very  much  used  in  the  excavation  of  earth  and  are  com- 
monly known  as  Judson  powder  (after  the  inventor),  bank  powder, 
or  railroad  powder.  In  the  analysis  of  low-grade  granular  powder, 
moisture  is  determined  by  the  standard  method,  and  the  usual 
method  of  extracting  with  ether  is  followed.  In  the  ether  extract 
are  usually  found  large  proportions  of  sulphur,  rosin,  etc.,  besides 
the  nitroglycorin.  The  proportion  of  sulphur  commonly  used  in 
64 


GRANULATED   NITROGLYCERIN    POWDER.  65 

low-grade  granular  powder  is  so  considerable  that  usually  it  is  not 
all  removed  by  extraction  with  ether. 

The  determination  of  nitrates  in  the  residue  after  ether  extraction 
is  made  in  the  manner  already  outlined  for  ordinary  dynamite;  an 
additional  extraction  with  carbon  disulphide  is  necessary  to  remove 
the  sulphur  not  extracted  by  means  of  ether. 

As  antacids  are  seldom  added  to  low-grade  granular  explosives, 
the  extraction  with  dilute  acid  may  generally  be  omitted;  but  if  the 
qualitative  examination  has  indicated  the  presence  of  an  antacid,  its 
determination  is  made  as  already  described. 

The  residue  remaining  after  the  extractions  with  ether,  water,  and 
carbon  disulphide  is  usually  bituminous  coal,  although  charcoal  or 
other  carbonaceous  material  may  be  found.  An  examination  under 
the  microscope  or  with  a  hand  magnifier  will  usually  show  with 
sufficient  certainty  the  nature  of  the  insoluble  residue,  and  the 
presence  of  bituminous  coal  may  generally  be  confirmed  by  a  vola- 
tile-matter determination  made  by  heating  the  solid  residue  in  a 
small  crucible  over  a  Bunsen  flame. 

The  separation  and  determination  of  the  ingredients  of  the  ether 
and  water  extracts  is  carried  out  by  the  methods  previously  described. 
67709°— Bull.  51—13 5 


BLACK  POWDER. 


The  general  term  "black  powder"  is  applied  to  several  explosives 
of  nearly  similar  composition,  including  chiefly  black  blasting  powder, 
black  gunpowder,  and  black  fuse  powder.  As  their  chemical  exami- 
nation involves  identical  problems,  they  are  here  treated  as  one 
general  class. 

Black  blasting  powder  usually  consists  of  a  mixture  of  sodium 
nitrate,  sulphur,  and  charcoal,  whereas  black  gunpowder  is  generally 
a  mixture  of  potassium  nitrate,  sulphur,  and  charcoal.  The  real 
difference  between  "gunpowder"  and  black  blasting  powder  is  one 
of  use,  since  some  blasting  pow^der  containing  potassium  nitrate  as 
the  oxidizing  material  has  been  made,  and,  similarly,  there  is  record 
of  gunpowder  having  been  made  from  sodium  nitrate.  Although 
black  blasting  powder  is  usually  made  in  larger  grains  than  gun- 
powder, yet  for  certain  purposes,  particularly  for  large  cannon, 
grains  of  gunpowder  have  been  made  even  larger  in  size  than  the  cus- 
tomary kinds  of  blasting  powder,  and  again  finely  granulated  blasting 
powder  has  been  made  for  use  where  a  quick-acting  explosive,  yet 
one  not  so  rapid  as  dynamite,  was  desired. 

The  black-powder  composition  used  in  the  ordinary  miner's  safety 
fuse  and  known  as  "fuse  powder"  is  much  similar  to  the  ordinary 
grade  of  gunpowder,  but  is  of  very  fine  granulation  (usually  40  to  100 
mesh),  and  contains  potassium  nitrate  as  its  oxidizing  agent. 

PHYSICAL  EXAMINATION. 
GRANULATION  OR   AVERAGE   SIZE   OF   GRAINS. 

The  determination  of  the  granulation  of  black  powder  is  made  by  a 
series  of  standard  sieves,  but  this  examination  is  not  usually  required 
in  connection  with  chemical  analysis,  and  can  be  made  only  where  a 
large  sample  of  the  powder  is  available.  The  standard  sizes  of  grains 
of  black  blasting  powder,  together  with  a  statement  of  the  size  of 
screen  through  which  the  material  will  pass,  is  given  in  the  following 
tabulation :  ° 

aMunroe,  C.  E.,  and  Hall,  Clarence,  A  primer  on  explosives  for  coal  miners.    Bureau  of  Mines,  Bull.  17, 
1911,  p.  17. 

66 


BLACK   POWDER. 

Relation  between  size*  of  black  blasting  powder  and  separating  sieve. 


67 


Diameter  of 

Diameter  of 

round  holes 

round  holes 

Size  of 

in  screens 

in  screens 

grains. 

through 
which  grains 

on  which 
grains 

pass. 

collect. 

CCC 
CC 

ttinch 
JJ  inch 

H  inch 
U  inch 

C 

ii  inch 

ii  inch 

F 

IS  inch 

i  J  inch 

FF 

JJ  inch 

»TT  inch 

FFF 

»*»  inch 

A  inch 

FFFF 

&  inch 

(a)  A  inch 

«  Or  28-mesh  bolting  cloth. 
GRAVIMETRIC  DENSITY. 

By  "gravimetric  density"  is  meant  the  "apparent  specific  gravity " 
of  the  explosive,  or  the  ratio  that  the  weight  of  the  powder  con- 
tained in  a  given  volume  bears  to  the  weight  of  water  that  would 
exactly  fill  the  same  volume.  Gravimetric  density  or  apparent 
specific  gravity  is  therefore  not  only  a  factor  of  the  true  density  of 
the  powder,  but  is  also  influenced  by  the  size  and  the  shape  of  the 
grains,  since  obviously  the  space  occupied  by  voids,  or  the  space 
between  grains,  must  vary  with  the  shape  and  size  of  the  grains. 

The  standard  determination  of  gravimetric  density  is  made  by 
pouring  the  powder  into  a  vessel,  usually  in  the  shape  of  the  frus- 
trum  of  a  cone,  striking  off  with  a  straightedge  all  over  that  required 
to  fill  the  measure,  and  then  weighing  the  powder  held  by  the  re- 
ceiver. Plate  II,  B,  shows  a  commercial  type  of  gravimetric  balance 
for  this  purpose.  With  this  balance  direct  readings  of  the  gravimetric 
density  of  a  powder  are  possible  without  calculation.  When  so  few 
determinations  must  be  made  as  to  make  the  use  of  a  separate  in- 
strument seem  unnecessary,  the  determination  of  the  weight  of 
powder  contained  in  a  cylindrical  graduate  of  known  volume,  or  a 
standard  pint  or  quart  measure,  may  be  made.  In  all  cases  the 
gravimetric  density  is  the  ratio  expressed  by  dividing  the  weight 
of  powder  required  to  fill  the  measure  even  full  by  the  weight  of  water 
from  the  same  measure  even  full. 

The  gravimetric  density  of  black  powders  varies  over  a  consid- 
erable range,  from  about  1  to  1.3. 

ABSOLUTE  DENSITY. 

By  "absolute  density "  is  meant  the  true  specific  gravity  of  the 
powder,  the  air  space  between  grains  being  disregarded  and  only  the 
density  of  the  grains  being  considered.  Owing  to  the  fact  that  both 
sodium  and  potassium  nitrates  are  readily  soluble  in  water,  it  is  not 


68 


ANALYSIS   OF   BLACK   POWDEE  AND   DYNAMITE. 


possible  to  make  this  determination  with  black  powder  by  the  picnom- 
eter  method  with  water,  so  that  a  number  of  instruments  involving 
the  use  of  mercury  have  been  designed  by  different  investigators. 

The  form  of  instrument  used  by  the  Bureau  of  Mines  is  illustrated 
in  figure  5,  and  was  devised  by  one  of  the  authors.0  The  apparatus 
consists  of  a  reservoir  and  means  for  introducing  within  this  reser- 
voir a  picnometer  bottle  con- 
taining the  powder  whose 
density  is  to  be  determined. 
By  opening  the  water-supply 
valve  the  mercury  is  raised 
within  the  reservoir,  and  on 
closing  it  and  opening  the 
waste-pipe  valve  the  water 
pressure  is  removed  from  the 
mercury  in  the  lower  reser- 
voir. A  Torricellian  vacuum 
is  thus  created  in  the  dome 
above  the  bottle;  most  of 
the  air  in  the  bottle  escapes 
and  is  replaced  with  mer- 
cury. The  operation  is  re- 
peated until  the  air  in  the 
bottle  is  completely  replaced. 
With  this  instrument  the  de- 
termination of  the  absolute 
density  of  black  powder  may 
be  quickly  and  accurately 
made. 

SAMPLING. 


FIGURE  5.— Densimeter. 


About  50  to  100  grams  of 
the  original  sample  is  crushed 
in  small  portions  in  a  porce- 
lain mortar  and  passed  through  an  80-mesh  sieve.  All  precautions 
are  taken  to  avoid  unnecessary  exposure  of  the  sample  to  the  air 
during  this  treatment.  If  each  portion  is  placed  in  a  stoppered 
bottle  as  soon  as  sifted,  there  is  no  appreciable  change  in  hygroscopic 
moisture  content.  The  powdered  sample  is  well  mixed  before  its 
analysis  is  begun. 

a  Snelling,  W.  O.,  Improved  densimeter.    Proc.  8th  Int.  Cong.  App.  Chem.,  vol.  4, 1912,  p.  105.     (Chem. 
Abs.,  vol.  6,  1912,  p.  3524.) 


BLACK   POWDER.  69 

CHEMICAL  EXAMINATION. 

The  chemical  examination  of  black  powder  consists  essentially  of 
the  determination  of  the  amounts  of  moisture,  nitrate,  sulphur,  and 
charcoal  present.  The  nitrate  is  readily  separated  from  the  sulphur 
and  charcoal  by  the  solvent  action  of  water,  and  after  the  residue  from 
water  extraction  has  been  carefully  dried  the  sulphur  may  be  readily 
separated  from  the  charcoal  by  the  action  of  carbon  bisulphide,  or 
other  solvent. 

The  charcoal  is  always  determined  by  difference.  After  being 
dried  the  charcoal  is  usually  ignited  and  its  content  of  ash  determined. 

DETERMINATION    OF    MOISTURE. 

The  determination  of  moisture  is  carried  out  exactly  as  has  been 
described  in  the  analysis  of  dynamite  (p.  20),  a  2-gram  sample  being 
spread  on  a  3-inch  watch  glass  and  desiccated  for  three  days  over 
sulphuric  acid.  It  is  customary  in  some  explosives  laboratories  to 
determine  moisture  on  a  sample  that  is  crushed  only  sufficiently  to  pass 
through  a  10  to  12  mesh  sieve,  because  in  further  pulverization  the 
moisture  content  of  the  powder  may  be  influenced  by  atmospheric 
conditions.  Comparative  determinations  have  indicated,  however, 
that  unless  there  is  undue  exposure  in  preparing  the  sample  the  differ- 
ence in  moisture  content  between  the  coarse  and  the  finely  powdered 
sample  is  slight,  and  since  the  nature  of  black  powder  is  such  that 
a  finely  powdered  sample  must  be  used  for  chemical  analysis  it  is 
considered  much  more  convenient  to  use  the  same  for  the  moisture 
determination. 

Many  authorities  recommend  that  moisture  in  black  powder  be 
determined  by  drying  in  an  oven  at  temperatures  of  60°  to  100°  C.a 
As  sulphur  is  more  or  less  volatile  at  temperatures  even  slightly  above 
ordinary,  the  authors  thought  it  advisable  to  compare  the  relative 
merits  of  oven  drying  with  the  desiccation  method.  A  series  of  deter- 
minations was  therefore  made  on  large,  well-mixed  samples  of  finely 
ground  powder  (80-mesh),  2  grams  spread  uniformly  in  a  thin  layer 
on  a  3-inch  watch  glass  being  used  for  each  determination.  The 
samples  heated  in  ovens  were  allowed  to  cool  for  15  minutes  in  desic- 
cators before  weighing.  It  was  found  necessary  to  make  the  weigh- 
ings as  rapidly  as  possible  in  order  to  prevent  increase  of  weight.  The 
following  results  were  obtained. 

a  Lunge,  O.,  and  Berl,  E.,  Chemisch-technische  Uutersuchungsmethoden,  voL  3,  1910,  p.  116;  Gutt- 
m..:in,  O.,  Schiess-  uud  Sprengmittel,  1900,  p.  48. 


70 


ANALYSIS   OF   BLACK   POWDER  AND  DYNAMITE. 


Results  of  determinations  of  moisture  in  black  powder. 

SAMPLE  A. 
[Determinations  by  W.  C.  Cope.] 


Time. 

Loss  on 
desiccation 
over  sul- 
phuric acid. 

Loss  on 

drying  at 

Loss  on 

drying  at 
100°. 

Hours. 
1 

Per  cent. 

Per  cent. 
1  00 

Per  cent. 
1  05 

2 

1.00 

1.10 

3 

1  00 

1.15 

5 

1.00 

1.30 

72 

1  00 

SAMPLE  B. 
[Determinations  by  C.  A.  Taylor.] 


1 

0  44 

0  57 

2 

.46 

.78 

3 

50 

.94 

5 

.£4 

1.07 

7 

.c9 

1.19 

24 
72 

0.  42—0.  47 
0  46—0  49 

.74 

3.70 

The  analysis  (calculated  moisture  free)  of  sample  B  was  originally 
as  follows:  Sodium  nitrate,  74.07;  sulphur,  10.09;  charcoal  15.84.  The 
sample  dried  24  hours  at  100°,  with  a  loss  of  3.70  per  cent,  was  ana- 
lyzed with  the  following  result:  Sodium  nitrate,  77.0;  sulphur,  6.53, 
charcoal  16.47.  It  is  therefore  evident  that  there  is  a  loss  of  sulphur 
from  black  powder  at  100°,  and  that  this  loss  is  appreciable  in  even  a 
few  hours'  heating,  whereas  at  70°  the  loss  for  periods  of  heating  up  to 
five  hours  is  approximately  the  same  as  the  moisture  determined  by 
desiccation. 

Desiccation  gives  practically  constant  weight  in  24  hours,  but  as  the 
loss  of  moisture  takes  place  more  slowly  in  coarser  samples,  a  uniform 
period  of  three  days  has  been  adopted. 

Sulphur  alone  is  slightly  affected  by  .temperatures  up  to  100°  C. 
A  sample  of  approximately  5  grams  of  powdered  brimstone  (80-mesh) 
was  desiccated  for  two  days  over  sulphuric  acid  without  loss  of  weight. 
It  was  then  dried  five  hours  at  70°  C.,  losing  only  0.003  per  cent; 
further  drying  for  five  hours  at  97°  caused  a  loss  of  only  0.01  per  cent. 

EXTRACTION    WITH    WATER;    DETERMINATION    OF    NITRATES. 

In  the  determination  of  nitrates  by  extraction  with  water,  about  10 
grams  of  the  finely  ground  sample  is  weighed  in  a  Gooch  crucible  with 
asbestos  mat  and  about  200  c.  c.  of  water,  in  successive  portions  of 
15  to  20  c.  c.  each,  is  drawn  through  the  sample  by  means  of  suction. 
The  complete  solution  of  the  nitrate  is  hastened  by  the  use  of  warm  or 
hot  water,  although  200  c.  c.  of  cold  water  is  usually  sufficient.  The 
final  portions  of  water  passing  through  the  crucible  should  be  tested 
for  soluble  nitrate  by  evaporation  on  a  glass  plate,  or  an  excess  of1 
strong  sulphuric  acid  containing  a  few  crystals  of  diphenylamine  may 


BLACK   POWDER.  71 

}>o  added  to  a  few  drops  of  the  water,  and  an  intense  blue  coloration 
will  indicate  the  presence  of  nitrate. 

The  extraction  is  made  on  duplicate  samples  as  with  dynamite. 
Af  ter  the  complete  removal  of  the  nitrate  the  crucibles  containing  the 
portion  insoluble  in  water  are  placed  in  a  drying  oven  at  a  temperature 
of  about  70°  and  dried  to  constant  weight,  usually  overnight,  although 
five  hours  is  generally  sufficient.  The  percentage  of  loss  of  weight, 
minus  the  moisture  content  found  as  described  above,  represents  the 
total  water-soluble  material,  and  includes,  in  addition  to  sodium  or 
potassium  nitrate,  a  small  amount  of  water-soluble  organic  material 
from  the  charcoal  and  the  impurities  in  the  original  nitrate,  such  as 
chlorides  and  sulphate.  An  aliquot  portion  of  the  water  extract  is 
evaporated  to  dryness  on  a  steam  bath,  treated  with  a  little  nitric 
acid,  again  evaporated,  heated  to  slight  fusion,  and  weighed.  (See 
p.  44.)  For  accurate  analysis  the  amounts  of  chlorides  and  sul- 
phates may  be  determined  in  separate  portions  of  the  water  extract 
and  the  true  nitrate  content  determined  by  difference,  or  a  direct 
determination  of  nitrate  may  be  made  with  the  nitrometer  on  a 
portion  of  the  extract,  as  previously  described. 

The  water  solution  should,  of  course  be  tested  to  determine  whether 
sodium  or  potassium  nitrate  is  present.  This  determination  is  con- 
veniently made  by  heating  to  redness  a  clean  platinum  wire  dipped 
in  the  solution,  and  observing  the  color  of  the  flame  through  several 
thicknesses  of  cobalt  glass.  Potassium  is  indicated  by  its  character- 
istic red  color,  and  the  yellow  of  the  sodium  flame  is  entirely  cut  off 
by  the  blue  glass.  Without  the  cobalt  glass  a  sodium  nitrate  powder 
should  give  an  intense  yellow  flame  and  a  potassium  nitrate  powder  a 
pale  pink  or  lavender  flame.  If  both  sodium  and  potassium  nitrates 
are  indicated,  a  determination  of  potassium  is  best  made  by  the 
sodium-cobalti-nitrate  method  of  Drushel,0  or  the  proportions  of 
sodium  and  potassium  nitrates  may  be  calculated  with  an  approxi- 
mate degree  of  accuracy  from  the  total  weight  of  nitrates  found  by 
evaporation  and  the  percentage  of  nitrogen  in  the  combined  weight 
of  these  nitrates  as  determined  by  the  nitrometer. 

The  following  illustrates  the  method  of  calculation  employed: 

Let  a  =  weight  of  both  nitrates. 

x  =  weight  of  sodium  nitrate. 
Then  a  —  x  =  weight  of  potassium  nitrate. 

Let  6  =  percentage  of  nitrogen  found  in  combined  nitrates. 
16.  47  =  percentage  of  nitrogen  in  sodium  nitrate. 
13.87  =  percentage  of  nitrogen  in  potassium  nitrate. 


Then  0.1  647x  +  0.1387  (a-x}=       - 

lUU. 


a  Bowser,  L.  T.,  The  determination  of  potassium  by  the  cobalti-nitrat*  method.    Jcur.  Ind.  and  Eng. 
Ctem.,  vol.  1,  1909,  p  791. 


72  ANALYSIS   OF   BLACK   POWDER  AND   DYNAMITE. 

Solving  for  x  gives  the  weight  of  sodium  nitrate  present  in  the  mix- 
ture, and  subtracting  this  from  the  total  weight  of  the  mixture  gives 
the  potassium  nitrate. 

EXTRACTION  WITH  CARBON  DISULPHIDE;  DETERMINATION  OF  SULPHUR. 

The  dried  and  weighed  material  leftjrom  the  extraction  with  water 
consists  of  the  sulphur  and  charcoal.  The  sulphur  is  determined  by 
loss  of  weight  on  extraction  with  carbon  disulphide  in  the  Wiley 
extraction  apparatus,  the  method  being  exactly  the  same  as  that 
used  in  the  extraction  with  ether. 

Because  of  the  fact  that  it  is  difficult  to  obtain  carbon  disulphide 
that  does  not  leave  a  residue  of  sulphur  on  evaporation,  it  is  not 
customary  to  evaporate  the  carbon-disulphide  extract  to  dryness  and 
weigh  the  sulphur  dissolved  from  the  powder.  This  may  be  done, 
however,  if  freshly  distilled  pure  carbon  disulphide  is  used. 

INSOLUBLE    RESIDUE,  CHARCOAL. 

The  residue  remaining  in  the  crucibles  is  weighed  directly  as  char- 
coal after  drying  to  constant  weight  at  about  100°. 

In  drying  the  crucibles  after  the  carbon  disulphide  extraction 
extreme  care  should  be  used  to  avoid  setting  fire  to  the  inflammable 
vapor  of  the  carbon  disulphide,  as  it  sometimes  happens  that  the 
heavy  vapor  from  the  crucibles  passes  down  to  the  flame  by  which 
the  water  oven  is  heated.  Carbon  disulphide  has  the  lowest  ignition 
temperature  of  any  material  not  containing  phosphorus,  therefore  in 
extracting  with  carbon  disulphide,  or  in  handling  the  crucibles  after 
extraction,  considerable  care  should  be  taken  to  avoid  proximity  to 
lights  or  fire. 

DETERMINATION    OF   ASH. 

The  ash  in  the  charcoal  is  determined  by  ignition  over  a  Bunsen 
burner  until  all  of  the  carbon  has  been  burned  off,  and  weighing.  The 
ash  is  usually  found  to  be  about  0.5  to  1  per  cent  of  the  total  powder. 
In  case  of  an  abnormally  high  ash  value  it  is  possible  that  the  extrac- 
tion with  water  was  incomplete,  leaving  some  nitrate  undissolved. 

The  sulphur  used  in  black  powder  is  almost  invariably  brimstone, 
flowers  of  sulphur  not  being  suitable  for  this  purpose  because  of  the 
invariable  presence  of  acidity. 

In  those  cases  where  flowers  of  sulphur  are  used,  however,  it  should 
be  noted  that  the  extraction  of  the  sulphur  with  carbon  disulphide 
will  be  incomplete.  Watts,a  Gody,6  and  other  authorities  have  called 
attention  to  the  fact  that  flowers  of  sulphur  always  contain  a  con- 

a  Watts's  Dictionary  of  Chemistry,  1905,  vol.  4,  pp.  606-610. 

»  Cody,  L.,  Traite  theDrique  et  pratique  des  matieres  explosives,  1907,  p.  99. 


BLACK   POWDER. 


73 


siderable  amount  of  insoluble  amorphous  sulphur,  often  amounting 
to  as  much  as  35  per  cent. 

Experiments  made  in   the  bureau's   explosives  laboratory  with 
samples  of  brimstone  and  flowers  of  sulphur  gave  results  as  follows: 

-Relative  solubility  of  flowers  of  sulphur  and  brimstone  in  carbon  disulphide. 


Weight  of 
sample. 

Loss  of 

weight  on 
extraction.*! 

Insoluble 
substances. 

Flowers  of  sulphur                 .                     ....            ............. 

Grams. 
(       1.0907 

Qranut. 
0.  7817 

Percent. 
23.21 

\        1.0450 
(        1.1238 

.7472 
1.1230 

28.50 
.07 

\        1.1004 

1.0996 

.07 

«  Extracted  two  hours  in  Wiley  extraction  apparatus  with  carbon  disulphide. 

In  view  of  the  fact  that  when  flowers  of  sulphur  are  present  the 
extraction  with  carbon  disulphide  is  incomplete,  some  authors  have 
recommended  the  use  of  hot  aniline  as  a  solvent  for  the  sulphur. 

The  solubility  of  sulphur  in  various  solvents  is  shown  in  the  follow- 
ing table:0 

Solubility  of  sulphur  in  100  parts  (by  weight)  of  various  solvents. 


Solvent, 

Tempera- 
ture. 

Parts  (by 
weight)  of 
sulphur 
dissolved. 

•a 

o 

23.99 

Do                              .                

15 

41.65 

Do                                                                                     

22 

46.05 

Do                                         

38 

94.57 

Do                                                         

•  55 

181.34 

26 

.965 

Do                                                         

71 

4.377 

23 

1.479 

Ether                                          

23.5 

.972 

99 

1.205 

Phonol               .               

174 

16.35 

130 

85.96 

a  Boiling. 

Of  these  solvents  carbon  disulphide  and  aniline  are  the  ones  that 
would  appear  to  be  of  greatest  practical  value  in  analysis.  Carbon 
tetra chloride,  chloroform,  and  benzene  have  also  been  used  with  success 
as  solvents  for  sulphur,  but  their  use  requires  long-con tinued  extraction. 

Experiments  have  been  made  hi  the  explosives  laboratory  of  the 
bureau  to  determine  the  suitability  of  aniline  as  a  solvent  for  sulphur 
in  the  analysis  of  black  powder. 

Extractions  of  both  flowers  of  sulphur  and  brimstone  with  aniline 
heated  to  130°  to  140°  showed  only  about  0.05  of  1  per  cent  insoluble 
material  in  each. 

•  Gody ,  L.,  Traite  th&mque  et  pratique des  matieres  explosives,  1907,  p.  85.    Biedermann,  R.,  Chemiker 
Kalender,  pt.  1, 1910,  p.  291. 


74 


ANALYSIS   OF   BLACK   POWDER  AND   DYNAMITE. 


Several  samples  of  black  powder  were  analyzed,  the  sulphur  being 
determined  by  means  of  extraction  with  hot  aniline,  and  the  results 
were  compared  with  those  obtained  by  the  usual  method  of  extraction 
with  carbon  disulphide.  The  extraction  with  the  aniline  was  made 
by  adding  10-c.  c.  portions  of  aniline,  previously  heated  to  130°  to 
135°  C.  to  the  crucibles  containing  samples  that  had  been  extracted 
with  water  and  dried  in  the  usual  manner,  the  hot  aniline  being  drawn 
through  by  suction;  this  treatment  was  repeated  from  5  to  12  times, 
using  a  total  of  50  to  125  c.  c.  of  aniline  in  different  determinations. 
The  last  portions  of  aniline  were  removed  by  washing  with  a  small 
amount  of  alcohol,  and  the  residue  dried  at  100°  C.  The  loss  of  weight 
was  considered  as  the  amount  of  sulphur  present. 

Comparative  determinations  of  sulphur  in  black  powder  by  extraction  with  carbon  disul- 
phide and  aniline. 


Sample 
No. 

Sulphur  extracted. 

With  car- 
bon disul- 
phide. 

With 
aniline 
(130°). 

2 
3 

13.  64 
9.99 

7.81 

13.79 
9.72 
7.74 

Each  of  the  above  figures  is  the  average  of  four  to  six  closely  agree- 
ing results.  This  comparison  shows  that  the  aniline  method  gives 
very  satisfactory  results.  Even  as  small  an  amount  as  50  c.  c.  of 
aniline  was  found  to  be  sufficient  for  complete  extraction  if  each  por- 
tion was  allowed  to  stand  a  short  time  before  sucking  dry.  The  aniline 
may  be  readily  recovered  by  distillation  and  used  repeatedly. 

A  series  of  experiments  were  made  to  determine  whether  any  differ- 
ence in  results  would  be  effected  by  extracting  the  sulphur  with  carbon 
disulphide  before  the  nitrate  was  extracted  with  water — that  is,  an 
inversion  of  the  order  of  the  extractions.  A  number  of  samples  of 
black  powder  were  analyzed  by  both  methods  with  the  results  noted 
in  the  following  tables.  For  comparison,  determinations  were  made 
of  the  sulphur  by  precipitation  as  barium  sulphate  after  oxidation 
with  nitric  acid  and  potassium  chlorate. 


BLACK    POWDER. 


75 


Results  of  analyses  of  black  powder. 

(Samples  A,  B,  and  C  analyzed  by  C.  A.  Lambert;  sample  D  analyzed  by  C.  A.  Taylor.) 
METHOD  1  (WATER  EXTRACTION  FIRST). 


Sample. 

Moisture. 

Water 
extract. 

Carbon 
disulphide 
extract. 

Insoluble 
residue. 

Sulphur 
determined 
as  BaSO4. 

Percent. 

Per  cent. 

Per  cent. 

Percent. 

Per  cent. 

A 

/         0.16 
\           .16 

69.76 
69.73 

13.64 
13.55 

16.44 
16.56 

13.55 

B 

.21 
.21 

74.07 
74.27 

10.09 
9.89 

15.63 
15.63 

10.05 

.36 

78.88 

7.87 

12.89 

C 

.36 

78.98 

7.68 

12.98 

7.89 

.36 

78.91 

7.89 

12.84 

.47 

73.84 

10.02 

15.67 

D 

47 

73  74 

10  06 

15  73 

.47 

73.79 

10.04 

15.70 

METHOD  2  (CARBON  DISULPHIDE   EXTRACTION  FIRST). 


A 

iO.16 
.16 

69.58 
69.57 

13.74 
13.80 

16.52 
16.47 

}        13.55 

B 

.21 
.21 

73.97 
73.92 

10.39 
10.44 

15.43 
15.43 

}        10.05 

C 

.36 
.36 

78.45 
78.54 

8.47 
8.49 

12.72 
12.61 

|         7.89 

.47 

73.91 

10.15 

15.47 

i 

D 

.47 

73.74 

10.25 

15.54 

L  

.47 

73.82 

10.20 

15.51 

1 

It  will  be  noted  that  in  every  case  a  greater  loss  was  obtained  on 
extracting  with  carbon  disulphide  when  such  extraction  preceded  the 
extraction  with  water  than  when  it  followed  the  extraction  with 
water.  That  a  more  correct  value  for  the  amount  of  sulphur  present 
is  ob tamed  by  first  removing  the  water-soluble  portion  of  the  powder, 
is  shown  by  the  results  of  the  gravimetric  determination  of  sulphur 
as  barium  sulphate.  The  latter  results  agree  closely  with  the  loss  on 
extraction  with  carbon  disulphide  after  removal  of  the  nitrate. 

The  differences  in  results  noted  above  are  not  readily  explained. 
That  both  sodium  and  potassium  nitrates  are  practically  insoluble  in 
carbon  disulphide  was  shown  by  extracting  a  number  of  dried  samples 
of  each  of  these  nitrates  with  this  solvent,  losses  of  only  0.01  to  0.05 
per  cent  being  obtained.  It  was  further  demonstrated  that  the  small 
amount  of  moisture  present  in  the  powder  samples  at  the  time  of  the 
extraction  with  carbon  disulphide  was  not  the  cause  of  the  high 
results  of  method  2.  This  was  shown  by  extracting  several  samples 
of  black  powder  with  carbon  disulphide  both  before  and  after  drying 
in  vacuum  desiccators.  On  correcting  all  results  to  the  sample  in 
original  condition  it  was  found  that  the  loss  on  extraction  was  prac- 
tically the  same  in  both  cases.  The  results  are  shown  in  the  table 
following. 


76 


ANALYSIS   OF   BLACK   POWDER  AND  DYNAMITE. 


Effect  of  moisture  in  black  powder  on  extraction  with  carbon  disulphide  before  removal 

of  nitrate. 

[Determinations  by  C.  A.  Taylor.] 


Sample. 

Moisture. 

Loss  on  extraction  with 
carbon  disulphide. 

Original 
sample. 

Desiccated 
sample. 

Original 
sample. 

Desiccated 
sample. 

E 
F 
G 

Per  cent. 
0.30 
.22 
.32 

Per  cent.  . 

Per  cent. 
13.82 
10.02 

7  94 

Per  cent. 
13.  93 
9.99 
7.92 

The  method  adopted  by  the  Bureau  of  Mines  for  the  analysis  of 
black  powder  is  as  follows: 

BUREAU  OF  MINES  METHOD  OF  ANALYSIS. 

Moisture  is  determined  by  desiccating  a  2-gram  portion  of  the 
80-mesh  sample  spread  uniformly  on  a  3-inch  watch  glass  for  three 
days  in  a  sulphuric-acid  desiccator.  Nitrates  are  determined  by 
extraction  with  water,  sulphur  by  extraction  with  carbon  disulphide, 
and  charcoal  by  weighing  the  dried  insoluble  residue.  The  soluble 
impurities  (sulphates,  chlorides,  etc.)  are  determined  separately  and 
a  direct  determination  of  nitrate  made  by  means  of  the  nitrometer. 

In  the  analysis  of  black  powder,  as  in  the  analysis  of  all  other  ex- 
plosives, the  Bureau  of  Mines  follows  the  standard  methods  outlined  in 
this  bulletin  except  when  the  presence  of  unusual  constituents  renders 
necessary  additional  separations  or  determinations  or  introduces  new 
difficulties.  As  these  conditions  are  seldom  met  in  the  analysis  of  the 
more  simple  explosives,  such  as  dynamite  and  gelatin  dynamite,  but 
are  not  infrequently  found  in  connection  with  short-flame  explosives 
intended  for  use  in  coal  mining,  they  will  be  taken  up  in  a  subsequent 
bulletin,  which  will  consider  the  analysis  of  permissible  explosives. 


PUBLICATIONS  ON   MINE  ACCIDENTS   AND  TESTS  OF 

EXPLOSIVES. 


The  following  Bureau  of  Mines  publications  may  be  obtained  free 
by  applying  to  the  Director,  Bureau  of  Mines,  Washington,  D.  C.: 

BULLETIN  10.  The  use  of  permissible  explosives,  by  J.  J.  Rutledge  and  Clarence 
Hall.  1912.  34  pp.,  5  pis. 

BULLETIN  15.  Investigations  of  explosives  used  in  coal  mines,  by  Clarence  Hall, 
W.  O.  Snelling,  and  S.  P.  Howell,  with  a  chapter  on  the  natural  gas  used  at  Pittsburgh, 
by  G.  A.  Burrell,  and  an  introduction  by  C.  E.  Munroe.  1911.  197  pp.,  7  pis. 

BULLETIN  17.  A  primer  on  explosives  for  coal  miners,  by  C.  E.  Munroe  and  Clarence 
Hall,  61  pp.,  10  pis.  Reprint  of  United  States  Geological  Survey  Bulletin  423. 

BULLETIN  20.  The  explosibility  of  coal  dust,  by  G.  S.  Rice,  with  chapters  by  J.  C.W. 
Frazer,  Axel  Larsen,  Frank  Haas,  and  Carl  Scholz.  204  pp.,  14  pis.  Reprint  of 
United  States  Geological  Survey  Bulletin  425. 

BULLETIN  44.  First  national  mine-safety  demonstration,  Pittsburgh,  Pa.,  October 
30  and  31,  1911,  by  H.  M.  Wilson  and  A.  H.  Fay,  with  a  chapter  on  the  explosion  at 
the  experimental  mine,  by  G.  S.  Rice.  1912.  75  pp.,  7  pis. 

BULLETIN  46.  An  investigation  of  explosion-proof  mine  motors,  by  H.  H.  Clark. 
1912.  44  pp.,  6  pis. 

BULLETIN  48.  The  selection  of  explosives  used  in  engineering  and  mining  opera- 
tions, by  Clarence  Hall  and  S.  P.  Howell.  1913.  50  pp.,  3  pis. 

TECHNICAL  PAPER  4.  The  electrical  section  of  the  Bureau  of  Mines,  its  purpose 
and  equipment,  by  H.  H.  Clark.  1911.  12  pp. 

TECHNICAL  PAPER  6.  The  rate  of  burning  of  fuse  as  influenced  by  temperature  and 
pressure,  by  W.  O.  Snelling  and  W.  C.  Cope.  1912.  28  pp. 

TECHNICAL  PAPER  7.  Investigations  of  fuse  and  miners'  squibs,  by  Clarence  Hall 
and  S.  P.  Howell.  1912.  19  pp. 

TECHNICAL  PAPER  11.  The  use  of  mice  and  birds  for  detecting  carbon  monoxide 
after  mine  fires  and  explosions,  by  G.  A.  Burrell.  1912.  15  pp. 

TECHNICAL  PAPER  12.  The  behavior  of  nitroglycerin  when  heated,  by  W.  O.  Snel- 
ling and  C.  G.  Storm.  1912.  14  pp.,  1  pi. 

TECHNICAL  PAPER  13.  Gas  analysis  as  an  aid  in  fighting  mine  fires,  by  G.  A.  Bur- 
rell and  F.  M.  Seibert.  1912.  16  pp. 

TECHNICAL  PAPER  17.  The  effect  of  stemming  on  the  efficiency  of  explosives,  by 
W.  O.  Snelling  and  Clarence  Hall.  1912.  20  pp. 

TECHNICAL  PAPER  18.  Magazines  and  thaw  houses  for  explosives,  by  Clarence  Hall 
and  S.  P.  Howell.  1912.  34  pp.,  1  pi. 

TECHNICAL  PAPER  19.  The  factor  of  safety  in  mine  electrical  installations,  by 
H.  H.  Clark.  1912.  14  pp. 

TECHNICAL  PAPER  21.  The  prevention  of  mine  explosions;  report  and  recom- 
mendations, by  Victor  Watteyne,  Carl  Meissner,  and  Arthur  Desborough.  12  pp. 
Reprint  of  United  States  Geological  Survey  Bulletin  369. 

TECHNICAL  PAPER  23.  Ignition  of  mine  gas  by  miniature  electric  lamps,  by  H.  H. 
Clark.  1912.  5pp. 

77 


78  ANALYSIS   OF   BLACK   POWDEK  AND  DYNAMITE. 

TECHNICAL  PAPER  24.  Mine  fires;  a  preliminary  study,  by  G.  S.  Rice.  1912. 
51  pp. 

TECHNICAL  PAPER  28.  Ignition  of  mine  gas  by  standard  incandescent  lamps,  by 
H.  EL  Clark.  1912.  6  pp. 

TECHNICAL  PAPER  29.  Training  with  mine-rescue  breathing  apparatus,  by  J.  W. 
Paul.  1912.  16  pp. 

MINERS'  CIRCULAR  3.  Coal-dust  explosions,  by  G.  S.  Rice.     1911.    22  pp. 

MINERS'  CIRCULAR  4.  The  use  and  care  of  mine-rescue  breathing  apparatus,  by 
J.  W.  Paul.  1911.  24  pp. 

MINERS'  CIRCULAR  5.  Electrical  accidents  in  mines;  their  causes  and  prevention, 
by  H.  H.  Clark,  W.  D.  Roberts,  L.  C.  Ilsley,  and  H.  F.  Randolph.  1911.  10  pp.,  3  pis. 

MINERS'  CIRCULAR  6.  Permissible  explosives  tested  prior  to  January  1,  1912,  and 
precautions  to  be  taken  in  their  use,  by  Clarence  Hall.  1912.  20  pp. 

MINERS'  CIRCULAR  9.  Accidents  from  falls  of  roof  and  coal,  by  G.  S.  Rice.  1912. 
16  pp. 

MINERS'  CIRCULAR  10.  Mine  fires  and  how  to  fight  them,  by  J.  W.  Paul.  1912. 
14pp. 

MINERS'  CIRCULAR  11.  Accidents  from  mine  cars  and  locomotives,  by  L.  M.  Jones. 
1912.  16  pp. 


INDEX. 


A.  Page. 

Abel  test  for  stability.     See  Stability,  Abel 
test  for. 

Ammonia  dynamite,  analysis  of 57, 58 

constituents  of 57 

Ammonia  gelatin  dynamite,  definition  of 56 

Ammonium  nitrate.    See  Nitrates. 

Antacid,  gravimetric  determination  of 47 

Ash,  in  black  powder,  determination  of 72, 73 

Ash,  in  dynamite,  determination  of 50 

B. 

"  Bank  powder, "  composition  of 64 

Berl,  K.,  and  Jurrissen,  A.  W.,  nitrogen-deter- 
mination method  of 63 

Black  blasting  powder,  definition  of 65 

Black  powder,  analysis  of,  method  of 76 

composition  of 06 

granulation  of,  determination  of 66 

sizes  of 67 

moisture  in,  determinat  ion  of 69 

results  of  analyses  of 75 

sample  of,  preparation  of 18 

Black  powder  and  gunpowder,  difference  be- 
tween    G6 

"  Blasting  gelatin, "  composition  of 54 


Calcium  in  dynamite,  determination  of 46 

Calcium  carbonate  in  dynamite,  determina- 
tion of 53 

Cartridge  of  dynamite,  construction  of 13 

volume  of,  determination  of 8 

Charcoal,  in  black  powder,  determination  of.  69-72 
Colophony.    See  Rosin. 

D. 

Densimeter,  description  of 68 

figure  showing 68 

Density,  absolute,  definition  of 67 

determination  of  apparatus  for 68 

Density,  gravimetric,  definition  of 67 

determination  of 7, 8, 67 

Desiccation  of  dynamite,  method  of 28, 29 

efficiency  of  agents  for 24 

time  required  for 20 

use  of  sulphuric  acid  in 20, 24 

use  of  vacuum  in 27, 28 

without  desiccating  agent,  results  of 26 

Desiccator,  Hempel,  efficiency  of 21 

Scheibler,  efficiency  of 21-24 

Dunn,  Col.  B.  W.,  work  of 9 

Dynamite,  analysis  of 7, 14 

variations  in  methods  of £0, 51 

results  of 51,57 

cartridge  of,  segregation  in 15 

composition  of 6 

definition  of 6 


Dynamite— Continued.  Page. 

moisture  in,  changes  of 15-16 

determination  of 19 

effect  of  temperat  ure  on 22-23 

figure  showing 23 

methods  for 19 

use  of  vacuum  in 27 

variations  in  method  of 52 

Pittsburgh  testing  station,  composition 

Of 5 

qualitative  examination  of 16-19 

sample  of,  preparation  of 12-16 

segregation  in 14 


Ether,  anhydrous,  extractive  power  of 33, 34 

as  extractive  agent,  use  of 40-41 

Extraction  of  dynamite  with  ether 30 

apparatus  for 30,31 

effect  of  moisture  on 34, 35 

methods  of 30-33 

Exudation  of  nitroglycerin,  centrifugal  test 

for 9, 10 

apparatus  used  in 9 

method  employed  in 9 

40°  test  for 8,9 

pressure  test  for 9 

F. 
Fuse  powder,  description  of 66 

G. 

Gelatin  dynamite,  composition  of 54 

moisture  in,  determination  of 54 

nitrocellulose  in,  determination  of 55 

preparation  of  sample  of 54 

sulphur  in,  determination  of 55 

Gody,  L.,  work  of 72 

Gravimetric  balance,  view  of 32 

Gunpowder,  composition  of 66 

H. 

Hempel  desiccator,  efficiency  of 21 

Hyde,  A.  L.,workof 40 

I. 
Infusorial  earth,  view  of 50 

J. 

Judson,  E.,  work  of 64 

Judson  powder,  composition  of 64 

Jurrissen  and  Berl,  method  of t>3 

L. 

Low-freezing  explosives,  constituents  of 61 

Lunge  nitrometer,  description  of 35, 36 

standardization  of 36, 37 

use  of 45 

view  of 38 

79 


80 


INDEX. 


Magnesium  in  dynamite,  determination  of. . .  46 

Merrill,  G.  P.,  work  of 49,50 

Moisture  in  dynamite.    See  Dynamite,  mois- 
ture in. 

Moisture  in  black  powder,  determination  of..  69 

results  of 70 

Munroe,  C.  E.,  work  of 5 

N. 

Nitrates  in  black  powder,  calculation  of 71, 72 

extraction  of 70, 71 

in  dynamite,  determination  of 44, 53, 58-60 

Nitrocellulose,  determination  of. 55 

Nitroglycerin ,  absorbents  for 6, 49 

classification  of 6 

determination  of..., 35 

apparatus  used  in 35, 36 

extraction  of,  with  ether 30 

test  for 16,17 

In  low-freezing  dynamite,  freezing  point  of      61 
Nitrosubstitution   compounds,    method    6f 

determining 62 

Nitrosubstitution  products,  color  reactions  of.        18 
color  test  for 17 

P. 

Potassium  in  black  powder,  determination  of.        71 
Potassium  nitrate.    See  Nitrates. 

R. 

Railroad  powder,  composition  of. 64 

Reflux-condenser  method  of  extraction 30-32 

Resin  in  dynamite,  determination  of 41,42 

S. 

Scheibler  desiccator,  efficiency  of 21, 24 

Segregation   in    dynamite.    See  Dynamite, 
segregation  in. 


Sodium  nitrate.    Sec  Nitrates. 

Specific  gravity,  apparent,  determination  of. .      7, 8 

Specific  gravity,  true.    See  Density ,  absolute. 

Stability  of  explosives,  Abel  test  for 10-12 

apparatus  used  in 11-12 

time  required  for 12 

Starch  in  dynamite,  determination  of,  appara- 
tus for 43 

method  of 47 

materials  included  in 47 

Sulphur  in  black  powder,  determination  of 72-74 

effect  of  temperature  on 70 

in  dynamite,  determination  of 41, 42 

extraction  of 30 

test  for 17 

solubility  of,  in  acetic  acid 42 

T. 

Trinitrotoluene  in  dynamite,  test  for 17 

U. 

Universal  tube  for  nitrometer,  advantage  of. .        38 

description  of, 38 

view  of 36 

W. 


Water.    See  Moisture. 

Watts,  work  of 

Wiley  extractor,  description  of. 

use  of. 

view  of 

Wood  pulp,  analyses  of. 

determination  of. 

examination  of 

view  of 

Wrampelmeier,  T.  J.,  work  of. . 


Z. 


Zinc  in  dynamite,  determination  of. 46, 58 


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